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 The pigment
colors --- black and red,
and the agouti genes --- bay, brown and solid (black),
combine to produce four dark, "pure" (undiluted) colors:
These are the dark
foundations
upon which all other horse colors are
built.
Other
genes, like white markings, the various dilutions, graying, roan and the
leopard complex (appaloosa), work by simply changing the
expression of these four pure, dark
colors.
Characteristics of the four dark base colors resulting from the
interaction of pigment and agouti, without any other known color
modifiers:
1. Chestnut (Red) = ee
plus any agouti A, At or a
 Body
color any shade of red, reddish-brown, or orangey-red; points may be lighter or
darker than the body, or the same color, but not true black. May be called sorrel.
Chestnut shades range from "blond" chestnut, which looks
palomino, to "sooty"*, or "liver" chestnut, which can
appear almost black.
2. Bay =
EE or Ee plus AA, Aa,
or AAt
 Body
color red or reddish-brown, ranging from light to dark; points black. Sooty*
bays may have an overlay of black hairs on the body, but the color
underneath will still be red.
3. Brown (aka Seal Brown) =
EE or Ee
plus AtAt
or Ata
 There
is now a DNA test to differentiate this color
combination from bay or black. The
typical brown is a black horse with tan highlights in
specific areas -- the muzzle, flanks, underbelly, and girth areas. Shades of (seal) brown
can range from almost all black to more like a "sooty* tan" horse.
4. Solid Black = EE
or Ee plus aa
 The
horse is black all over, including the muzzle, flanks and underbelly. Blacks
may fade when exposed to the sun, but the new coat comes
in true black, after each shedding. Black seems to also come in "shades":
from a nearly blue-black that never fades, to "fading black",
which comes in true black but lightens to red when exposed to
the elements, to "light black" **,
which always has a brownish cast to it, and can even look
tan on large areas of the body.
**A word about "light
black", which has only been tentatively identified in a few equine
families. This does not refer to the variation in black caused by the
leopard complex (Appaloosa) genes, or by fading. A true "light black" horse
tests as a solid black, with no other known
dilutions or color modifiers, yet has no truly black hair anywhere on its
body; even when the new coats come in, the hair is all various shades of
brown or tan. It remains to be seen what causes this, genetically.
*
Sooty, sootiness, smutty, smuttiness, shaded,
shading: not yet understood genetically, "sooty"
"smutty" or "shaded" are all descriptive terms for a horse's
"red" areas being covered, to varying degrees, with
darker, or even black-looking hairs.
Review/summary
Pigment:
E and e are the pigment genes
E = black pigment present, and is dominant over
e
e = red pigment only, but is only expressed if
the horse is ee
Agouti:
A, At, and a
are the agouti genes,
only affecting
black pigment (E)
A = bay, and is dominant over the other two agouti genes
At = brown, and is recessive to bay
but dominant
over solid black
a = solid black, and is recessive to the other two agouti
genes, and so only expressed if the horse is aa
-
The next genes this site will explore
are the DILUTION
genes.
Click Dilutions to
learn about
Cream, Dun, Silver,
Champagne, and Pearl
...or, you may want to skip to another
set of color modifying genes
of particular interest to you.
You may use any of the buttons at the top or bottom of this page
to find the page you
want.
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