Southwest Spanish Mustang Association  
"Heritage Horse of Oklahoma"
Preserving The Purest
Spanish Mustangs
In Existence Today
by D. Phillip Sponenberg,  DVM, PhD.
Virginia-Maryland Regional College of Veterinary
Medicine,  Virginia Tech
Blacksburg, VA  24061
Color Genetics
Horse color genetics is a complicated subject. It is impossible to deny that the
pieces it is possible to begin to understand how the interactions of different factors result
in the vast array of color in horses.  A first step is to separate out white spots or hairs.
Only concentrate on color. Following an appreciation of how the colors arise it is possible
to add the white, thereby understand the final combinations.
Color is the result of interaction of eleven or so different factors. Some of these are
single genes, others are unknown genetically. Each unique combination results in a single
color, so there are many, many possibilities. Some are common, some are rare, and
some depend
Genetic Control Of Color
(Ignore The White!)

The three main colors of horses are bay, chestnut, and black.  
All other colors can be built from these three,
so understanding these three is the foundation for all of the others.
Chestnut #1
nonchestnut (black or bay) (EE ).
Chestnut horses are basically red,
although many have  "Bend Or" spots,
which are dark or black spotsup to a
few inches across.
Bay#2.
For the nonchestnut horses, bay (A+ ) is
dominant to black (Aa ).
This relationship is tricky. Chestnut, though
recessive, masks whether a horse would have
been black or bay. A mating of chestnut and
black horses can result in bay foals, even though
both chestnut and black are recessive to bay.
Bay
Light Version
Chestnut
Blood bay,
Mahogany bay
Red bay, Cherry bay
Red chestnut
Medium Version
Sandy bay, Gold bay
Dark Version
Black
Black
Liver Chestnut
Gold or Light Chestnut
Color
Black
“Summer” Black
Shade #3
"Shade" is a complicated trait that is probably controlled by several genes rather than a few.  "Shade", for
convenience, can be considered to make the base color dark, medium or light.  It interacts with the basic
coat colors to produce more designations:
Chestnut
Brown or Mahogany Bay (depending on naming system)
Bay
Base Color
Liver Chestnut or Black Chestnut
Sooty Variant
Black
Black
Sooty #4
"Sooty" is a factor that adds black hairs into the base color. This changes the
appearance from a clear color to a sooty color, and in some systems of color names
will change names of some colors.The interaction of sooty and shade provide many,
many different nuances of color.
#5
The mane and tail color on chestnut horses is variable.  It ranges from a dark brown that is close to black, through bright
reds, and on to the very pale flaxen colors that are nearly white.  These changes are related to many, many different genes
and are complicated.
Mealy #6.
Mealy is a single, dominant gene (Pa+ )
which causes lighter areas on the belly, muzzle, inner legs,
and over the eyes. It is usually ignored in color description, except for changing
black to seal brown, and changing chestnut to sorrel for breeders of draft horses.
Smoky
Sooty
Palomino
Cream #7.
dilutes red to yellow, and leaves black unaffected.  With two doses
it changes both red pigment and black pigment to cream, with pink skin and blue eyes.
Bay
Two Doses
Cream (technically
perlino)
Brown
Palomino
Cream (technically
cremello)
Cream (technically
cremello)
Cream (technically
smoky cream)
Buckskin
Liver
Chestnut
Cream (technically
perlino)
One Dose
Base Color
Black
Sooty
Buckskin
Chestnut/Sorrel
Base Color
Apricot Dun
“Light” Black
Gold Dun
Sorrel
Coyote Dun
Linebacked Cream
Chestnut
Grullo
Dun Variant
Buckskin
Zebra Dun
Olive Dun or Olive Grullo
Black
Linebacked Palomino
“Sooty” Black
Brown
Bay
Red Dun
Cream
Lobo Dun
Palomino
Dun # 8
The linebacked dun gene (Dn+ ) is dominant.
It lightens body color,
leaving a stripe down the back, bars on the legs,
and frequently a stripe on the withers.
Silver Dapple Variant
Linebacked Yellow Silver
Chestnut
Yellow Silver
Buckskin
Bay
Chestnut (no visible evidence)
Red  Silver
Brown
Black
Chocolate Silver, Blue Silver, Silver Dapple
Brown Silver
Base Color
Zebra Dun
The silver dapple gene (ZZ ) is a dominant that acts to lighten black areas, and leaves red
that are frequently confused with chesnut, but that lack the redness of chestnut. It lightens
manes, tails, and lower legs to flaxen, or can leave them relatively unchanged.
I haven't found any
examples of SSMA horses
with the Silver Dapple
gene. I'll keep looking.
Palomino
champagne
base color
champagne variant
Black
gold champagne (mimics
palomino or light sorrel)
Champagne #10 .
The champagne gene (ChC ) is a dominant that
is Lightens black areas to flat light chocolate,
Skin to be pink or mottled, and eyes haz
vory champagne (very light, with
dark blue eyes)
amber champagne (gold or yellow
with brown points)
Grullo Brindle
Brindle #11
The final color interaction is brindle.
This is rare indeed,
and reorganizes the sooty countershading
into vertical stripes.
Base Color