I agree with others. If you're breeding for color, don't breed.
Look for a nicely bred, athletic built foal in the ground with parents that prove the babies lineage! The only 100% guarantee for a true buckskin.
NOTE: I bred my sorrel mare to a homozygous black and white stallion. I read the paperwork. You know what I got? A bay and white foal! I don't care about the color, but it's an example!