Help me figure out what kind of appy cross I have...?

I read in a book that for an appy mare to show color she has to be zygous dominate for that gene. For an appy colt to show color it can be zygous or heterozygous. Mare: ApAp, colt ApAp or Apap. apap in either will not show color at all. The book was called Equine Color Genetics and it was published in the late 90's. New research might have come out with a different theory since I read that book, however.