Blue, Splash & Black Chicken Genetics · Chicken Color Standards

Blue, Splash, and Black are not three separate colours — they are the three genotypes of a single gene, the Blue locus. Grasp that one fact and two things that puzzle a lot of breeders fall into place: why a blue-to-blue mating never gives an all-blue hatch, and how to set up a pen that does. For the wider system these terms sit in, see the Genetics Guide.

Blue Brahma rooster, slate-grey body with darker hackle and tail, feathered legs. — Blue rooster — the sire. The Blue gene dilutes black to slate-grey, leaving hackle and tail darker.

Blue Brahma hen with even slate-blue body feathers, feathered legs. — Blue hen — his daughter, out of the black hen shown next. She carries one copy of the Blue gene from her sire.

Black Brahma hen with a green sheen, feathered legs. — Black hen — the dam. Black is the base: Blue is black plus one Blue gene, Splash is black plus two.

Black chick with a white throat patch, held in a hand. — A black chick — the white throat patch at this stage is normal down variation, not a sign of mottling.

Close-up of two black Brahmas with iridescent green-black plumage. — Iridescent green-black plumage on two black Brahmas.

One gene, three genotypes

The Blue locus (Bl) has two alleles: bl+ (the ordinary non-blue version) and Bl (blue). What makes it interesting is that it shows incomplete dominance — the heterozygote looks intermediate, so each copy of Bl is visible:

Genotype	Name	What you see
`bl+/bl+`	Black	No dilution — full black (eumelanin).
`Bl/bl+`	Blue	One copy dilutes black to an even blue-grey.
`Bl/Bl`	Splash	Two copies dilute further — a pale bird flecked with blue-grey.

Blue dilutes only eumelanin (black pigment). Any red or gold on the bird comes from pheomelanin, which Bl leaves untouched — so a "blue" bird built on a gold or partridge base keeps its ground colour, and only the black parts turn blue-grey. That single-pigment action is the key difference from lavender, which dilutes both.

bl⁺/bl⁺ vs Bl/bl⁺ vs Bl/Bl

bl⁺

→

Black — no dilution

bl⁺

→

Blue — one copy dilutes

→

Splash — two copies dilute further

Why blue never breeds true

Because Blue is a heterozygote (Bl/bl+), you cannot fix an all-blue line — mating blue to blue reshuffles the single Bl alleles every generation. The result is the classic 1 : 2 : 1:

Blue × Blue → 25% Black : 50% Blue : 25% Splash. Every blue-to-blue hatch throws roughly a quarter black and a quarter splash. There is no genotype that gives "pure blue" offspring, because blue is the heterozygote.

The full set of crosses follows directly from that:

Cross	Offspring
Black × Black	all Black
Splash × Splash	all Splash
Blue × Blue	25% Black · 50% Blue · 25% Splash
Blue × Black	50% Blue · 50% Black
Blue × Splash	50% Blue · 50% Splash
Splash × Black	100% Blue

The breeder's shortcut: if you want a pen that produces only blue chicks, cross Splash × Black. Every chick gets one Bl from the splash parent and one bl+ from the black parent, so every chick is Bl/bl+ — blue. It is the one mating in the table with a single, uniform outcome you actually want.

You can run any of these — and add other genes on top — in the Breeding Outcomes tool, which will build the Punnett square and the frequency table for you. Open it with a cross already loaded: Blue × Blue, or the shortcut Splash × Black. You can also line the varieties up side by side in Compare (Blue vs Splash).

Don't confuse it with…

Lavender (self-blue). Lavender also softens a bird, but it is recessive and dilutes both pigments, so the red/gold washes out too. Blue leaves red/gold bright. See Lavender genetics for the full comparison.
Paint. Splash and Paint can look alike, but Paint is the Dominant White gene (I) layered over a blue/splash base — a different gene entirely. See the FAQ for the Splash-vs-Paint distinction, or put both standards side by side in Compare.

References & notes

The 1:2:1 behaviour of Blue is standard incomplete-dominance genetics; the cross ratios above are basic Mendelian expectations. Plumage-pigment framework: Smyth JR Jr (1990) Genetics of plumage, skin and eye pigmentation in chickens, in Crawford RD (ed.) Poultry Breeding and Genetics, Elsevier.
Blue is described here by its inheritance pattern; its molecular basis is less firmly established than loci given gene names elsewhere on this site. See the Genetics Guide references for the primary molecular literature on the other loci.

Try it: run a blue cross · compare with lavender · read the Genetics Guide