I don't think blue eyes are due to a pinto gene. I will keep looking, but this is what I have found so far:
http://www.madsci.org/posts/archives/feb20...76183.Zo.r.html
Here are two websites from which I borrowed this information:
http://www.champagnehorses.com/what_champagne_is-not.htm
http://www.champagne-horse-assoc.org/ichr_index.htm
Apparently, blue eyes in horses is often related to the horse having the
Champagne color modifying gene..or, possibly, one of the other
dilution-type genes. So, the rarity of horses having blue eyes might relate
to the rarity of dilution-type genes among the population of horses.
Genes are passed from the parents to the child; the champagne gene is
a dominant, dilution-type gene.
* "Dominant means that if it is present, it will manifest fully. A horse with
one Champagne gene looks no different from a horse with two
Champagne genes.
* Dilution means that it doesn't change the color of the horse, but lightens
the skin color...making the color "diluted". Dilution also affects eye color.
Champagne is ONE of the FOUR known dilution genes in horses. The
others are Creme (that makes Palomino, Buckskin, etc.); Dun; and Silver
Dapple.
Champagne is currently found primarily in Tennessee Walking Horses,
Missouri Foxtrotters, American Saddlebreds and Quarter Horses - also in
crosses and related breeds (Appaloosa, Paint, Part-Arabians, etc.).
The Champagne gene seems to function in many ways aside from simply
diluting a horse's coat color ... it also affects skin and eye color. Because
the Champagne gene is a simple dominant, your horse MUST have at
least one Champagne parent in order to be a Champagne!
Champagnes are born with bright pink skin and bright blue eyes that take
a long time to change, but usually become hazel or amber by adulthood.
Some [other] dilutes are also born with bluish eyes, but, again, these
begin to change rapidly instead of the slow change that Champagnes do.