Blue vs. Lavender Chicken Genetics: Why the Difference Matters in a Breeding Program

Blue and Lavender (also called Self-Blue) are two of the most popular color varieties in chickens, and two of the most often confused. Both turn black feathers a soft gray or blue-gray, and at a glance the birds can look very similar. Genetically, though, they are produced by two different genes that are inherited in different ways and affect pigment differently.

Understanding those differences is essential for breeders deciding which birds to bring into their program. One question that comes up often is whether Blue birds can be used to improve Lavender, and the short answer is no. The two genes can technically be combined, but doing so doesn't improve Lavender, and it makes the line much harder to manage. This article walks through Blue vs. Lavender chicken genetics, including how each gene works, why Blue and Lavender shouldn't be crossed, and why a carefully selected black bird is the better outcross for improving feather quality and color in Lavender.

The table below summarizes the main differences. Each one is explained in more detail in the sections that follow.

Key Terms In Blue vs. Lavender Chicken Genetics

A few genetic terms come up throughout this article:

• Gene and allele: A gene is a section of DNA that controls a trait. Alleles are the different versions of a gene. Every chicken inherits two alleles for each gene, one from each parent.

• Locus: The location of a gene on a chromosome. Blue and Lavender are at different loci, so they are inherited independently of each other.

• Wild type: The original, unmutated allele, written with a ⁺ (for example, bl⁺ or lav⁺).

• Dominant, recessive, and incompletely dominant: A dominant allele shows its effect with one copy. A recessive allele only shows its effect with two copies. An incompletely dominant allele has a partial effect with one copy and a stronger effect with two.

• Split: A bird that carries one copy of a recessive allele without showing it.

• Dilution gene: A gene that lightens pigment rather than changing its pattern.

• Eumelanin and pheomelanin: The two main pigments in chicken feathers. Eumelanin produces black; pheomelanin produces red, gold, and brown.

• Outcross: Breeding to a bird from outside the line to bring in traits the line needs.

How Blue Is Inherited

Blue is produced by an incompletely dominant dilution gene, written Bl. Because it is incompletely dominant, the number of copies a bird inherits determines how much its black pigment is diluted. Breeders call this the Blue, Black, and Splash (BBS) system, because the gene produces three possible results:

• Black (bl⁺/bl⁺) has no copies of the Blue allele, so its black pigment is not diluted.

• Blue (Bl/bl⁺) has one copy, which dilutes black feathers to blue or slate gray.

• Splash (Bl/Bl) has two copies, which dilute much more strongly and usually produce pale feathers with irregular blue or gray splashing.

Since a Blue bird carries one Blue allele and one wild-type allele, it passes on either one with equal chance. That is why two Blue birds bred together average about 25% Black, 50% Blue, and 25% Splash, and why Blue never breeds true. Breeding a Splash to a Black is the most reliable way to produce Blue, since every chick receives one Bl from the Splash parent and one bl⁺ from the Black parent.

Blue genetics chart showing the three BBS genotypes and the expected offspring of Black x Black, Black x Blue, Blue x Blue, and Blue x Splash matings

Blue birds bred to the APA Standard are also laced, with darker edging on each feather. Research points to three additional genes behind that lacing: Pattern (Pg), Melanotic (Ml), and Columbian (Co). Blue cockerels also usually have darker hackles, saddles, and wing bows. These traits are correct for a Blue variety, but as the section on combining the two genes explains, they cause problems when Blue is brought into a Lavender line.

How Lavender (Self-Blue) Is Inherited

Lavender, called Self-Blue in the APA Standard, works very differently. It is caused by a recessive point mutation in the MLPH (melanophilin) gene, identified by Vaez and colleagues in 2008. Because it is recessive, a bird needs two copies, lav/lav, to show the dilution.

A bird with only one copy, lav⁺/lav, is called a Lavender split. Depending on its genetic background, a split may look black or show other colors and patterns, but it won’t look Lavender. That is the key difference between the two genes, since Lavender can be carried unseen for generations while Blue always shows when it’s present. Neither gene is sex-linked, so it makes no difference whether the rooster or the hen is the carrier.

When two Lavender birds are bred together, both parents can only pass on lav, so every chick is Lavender. The chicks won’t all look identical, because other genes still affect patterning, pigment distribution, and color intensity. But Lavender breeds true, and that predictability is what allows a breeder to build consistency in a line.

Lavender genetics chart showing Black, Black Split, and Lavender genotypes and the expected offspring of Lavender x Lavender, Black x Lavender, Split x Split, and Split x Lavender matings

Because a split looks the same as a black bird, there are only two ways to find out whether a black bird carries Lavender: a test mating or a DNA (PCR) test. For a test mating, breed the bird to a Lavender. If it is a split, each chick has a 50% chance of being Lavender, so a single Lavender chick confirms it. If seven chicks hatch and none are Lavender, the chance that the bird is a split drops below 1%. Because the MLPH mutation behind Lavender has been identified, a PCR test can also confirm whether a bird is a split from a feather or blood sample, without waiting for a hatch.

How Each Gene Affects Feather Pigment

The two genes also differ in which pigments they dilute. Blue dilutes eumelanin (black) but leaves pheomelanin (red and gold) mostly unchanged. That’s why a Blue Copper Marans can have a blue body with rich copper hackles. Lavender dilutes both pigments, so black becomes lavender-gray and red or gold softens to cream, beige, or straw.

Dilution hides pigment, but it doesn’t remove the genes that produce it. A Lavender bird with pale cream markings may still carry gold that would be obvious without the dilution, and adding Blue does nothing to correct that, since it simply lays a second dilution over the same underlying color. Improving color means working on the pigment genetics underneath, which is why the choice of outcross matters so much.

Telling Blue And Lavender Apart

There are a few visual clues that help, although breeding records are always more reliable than appearance. Blue tends toward a slate tone with uneven shading, and its feathers often show darker lacing or edging, while Lavender is usually a more even, silvery gray over the whole bird. The difference is often easiest to see in the males, since Blue cockerels usually have noticeably darker hackles, saddles, and wing bows, and a well-bred Lavender male is much more uniform. Any red or gold on the bird is another clue. On a Blue bird those areas stay rich, while on a Lavender bird they soften to cream or straw.

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Left to right: a Blue Copper Marans hen, a Blue Copper Marans rooster, and a Lavender Birchen Marans hen and rooster. The Blue birds show slate-gray feathering with darker edging, and the Blue rooster keeps rich copper in his hackles and saddle. The Lavender birds are a more even, silvery lavender-gray over the whole body.

Why Blue and Lavender Shouldn’t Be Crossed

To understand why Blue and Lavender shouldn’t be crossed, it helps to know that they sit at separate loci. In other words, they are two different genes located in two different places in the chicken’s DNA. Every chicken has both genes, and at each one it inherits two alleles, one from each parent. A bird’s color depends on the combination it carries at both loci at once.

This means a single bird can carry Blue and Lavender together. A Lavender bird can also carry a copy of Blue, written Bl/bl⁺ lav/lav. A Blue bird can also be a Lavender split, written Bl/bl⁺ lav⁺/lav. In each case, the first pair of letters describes the Blue locus and the second pair describes the Lavender locus.

Because the two genes act independently, they don’t cancel each other out, and one doesn’t replace the other. Instead, their effects stack. Think of two dimmer switches controlling the same light. Lavender turns down both black and red or gold pigment, and Blue turns down black pigment a second time. Adjusting one switch doesn’t reset the other, so a bird carrying both is diluted by both.

The result is often a paler, sometimes uneven color. Because Lavender has already lightened the bird, the extra dilution from Blue can be subtle and easy to miss, which is one reason a Blue Lavender bird can pass for plain Lavender.

The two genes are also inherited independently, so whether a chick receives Blue from a parent has no bearing on whether it receives Lavender. Crossing them therefore produces several different combinations in the offspring rather than a simple blend, as the example below shows.

Following a Blue-to-Lavender cross through two generations shows why it causes problems. When a Lavender bird is crossed to a typical Blue bird that doesn’t carry Lavender, the first generation averages 50% Blue and 50% non-Blue. None of the chicks look Lavender, but every one of them carries a copy of it, and about half also carry Blue.

A breeder trying to recover Lavender would then breed those Blue splits back to Lavender.

That mating averages:

Half of the chicks that look Lavender would carry Blue, and Blue Lavender birds can be hard to tell apart from plain Lavender by eye. This is how Blue can end up in a Lavender line without the breeder realizing it.

If you suspect a Lavender bird carries Blue, breed it to a black bird with no Blue. A Blue Lavender bird will produce about 50% Blue-looking chicks from that mating, while a plain Lavender will produce none.

The American Poultry Association discourages crossing Blue into Self-Blue when breeding toward the Standard and gives three reasons:

1. Lavender doesn’t override other diluters, so the two genes together produce a very pale color that doesn’t meet the Standard. Two Self-Blue birds that both carry Blue can produce even more dilution, with splash spots.

2. The Pg, Ml, and Co genes a Blue bird often carries can cause partial or incomplete lacing in the offspring.

3. Melanizers carried by Blue birds give cockerels darker hackles, saddles, and wing bows, which the Self-Blue Standard doesn’t allow.

If Blue has already been introduced into a Lavender line, it can be bred back out, because the two genes are inherited separately. Removing it, though, takes several extra generations of test matings and careful selection, so it’s far better to keep Blue out of a Lavender line from the start.

The effects also may not show right away. A first-generation bird can look beautiful while carrying combinations that only appear when it’s bred. With more than one dilution gene involved, it becomes harder to tell which genes are producing the color you see. This also affects anyone who later buys birds from the line. Someone purchasing Lavender stock can reasonably expect a line built on recessive Lavender, not a mix of dilution genes. Accurate records and openness about outcrosses help other breeders know what they’re working with, and even after Blue is bred out, other genetics from that outcross may remain in the line.

Why Black Is A Better Outcross For Lavender

When a Lavender line needs improvement, a carefully selected black bird is usually a more useful outcross than a Blue one. Black has long been used in Lavender breeding to improve feather quality, strengthen breed type, and add genetic diversity, and it does all of this without adding a second dilution gene.

Feather quality is one of the most common reasons to outcross. Many Lavender lines tend toward weaker, more brittle feathers, and a black bird with strong, well-structured feathering can bring that quality back into the line.

A black outcross can also improve color. Because Lavender only dilutes the pigment a bird already has, it can’t turn uneven color into even color. A black bird with deep, even pigment and no red or gold leaking into the black gives the Lavender gene a clean base to work on, and over several generations this tends to produce a more even Lavender with fewer straw or brassy tones. Blue can’t offer the same benefit, since it adds another dilution on top of whatever pigment problems are already present.

The cross itself is straightforward. A Lavender bred to a black bird that doesn’t carry Lavender produces all Lavender splits, and breeding those splits back to Lavender produces about 50% Lavender chicks that keep the traits the outcross brought in.

Not every black bird makes a good outcross. Black birds can carry unwanted patterning genes and pigment modifiers too, so lineage, feather quality, breed type, and underlying color genetics should all be considered.

A genetically black bird from a BBS program doesn’t carry Blue. Unlike recessive Lavender, Blue can’t hide in a black bird, so a well-chosen black from a BBS background can be a reasonable outcross. A very dark Blue can occasionally be mistaken for Black, however, so breeding records or a test mating are worth having.

As an example, in my own Lavender Birchen Marans I outcross to Black Silver Birchen birds selected for the feather structure, pattern expression, and breed characteristics I want to strengthen. Blue has never been part of that program.

Matching The Outcross To The Problem

Breeding Lavender involves more than producing a chicken with gray feathers. Color consistency matters, but so do feather quality, correct breed type, overall structure, and the right expression of the variety’s pattern. Before choosing an outcross, it helps to identify what the line actually needs:

• If feather quality is weak, look for a black bird with strong, well-structured feathering.

• If unwanted warm tones or uneven color are showing up, look at the underlying pigment genetics and select breeders, including any black outcross, with clean, even pigment.

• If breed type needs work, choose the outcross for those physical characteristics.

Adding Blue because it also produces gray feathers doesn’t address any of these needs. A well-planned outcross brings in something the line is missing, rather than genetics that will have to be removed later.

The Bottom Line

Blue and Lavender may look alike, but they are two different genes that behave in very different ways. Blue is incompletely dominant and never breeds true, and it dilutes only black pigment, while Lavender is recessive, breeds true, and dilutes red and gold as well as black. Crossing the two adds a second dilution gene that can hide in Lavender-looking birds and interfere with even color and lacing, and it can take several generations to remove.

When a Lavender line needs better feathering or cleaner, more even color, the most useful outcross is usually a carefully selected black bird. A black bird with strong feather structure and deep, even pigment can bring in the qualities the line is missing without adding a second dilution gene. Its first-generation offspring will all be Lavender splits, and when those splits are bred back to Lavender, about half of the next generation will be Lavender again, carrying forward the improvements the outcross brought in. Because only one dilution gene is involved, the results stay predictable and are much easier to evaluate from one generation to the next.

Two birds can look almost identical and still carry very different genetics, and often you won’t see the difference until they’re bred. That’s why it pays to understand the genetics behind a bird’s color before deciding how to use it. For Lavender breeders, that means keeping Blue in its own program, choosing each outcross because the line needs what that bird brings, and keeping honest records. When you do, the birds you raise, sell, or share are what they appear to be, and the breeders who get them can build on them with confidence.

Sources

• Helton, L. (2021). Breeding Poultry with the Blue Gene. American Poultry Association.

• Vaez, M., et al. (2008). A single point-mutation within the melanophilin gene causes the lavender plumage color dilution phenotype in the chicken

Heidi Miller and her husband Jim are the founders of Seeking Eden Permaculture, a rare breed and permaculture farm nestled in the foothills of Central California. With over two decades of hands-on experience, Heidi has dedicated herself to preserving and improving a wide variety of rare breeds and color varieties — including her carefully developed line of Lavender Birchen Marans — with a passion and patience that is reflected in every carton of hatching eggs she produces.