Some of the Palomino registries even specify the amount of dark hair they will allow for registration purposes. This gene is often associated with dappling . If the horse has white markings, such as a blaze or stocking, you can still usually see the white against the cream coat. Palomino and Buckskin foals are often born a lighter color than they will shed out to be, and mature horses will often become lighter in the winter - palominos will sometimes even resemble a cremello, but their eyes are brown or hazel instead of blue. Palominos and Buckskins can vary widely in shade.
Buckskins can also vary widely in shade.
Horses with stripes are considered by AQHA to be one of the dun colors. It is not the same as the dun factor type, which is accompanied by leg barring and other primitive markings. These two different dilution genes interact to produce the lighter shades of dun, claybank, and palominos with dorsal stripes. Just because he is registered as a red dun does not change the fact he is also genetically a palomino. At this time they just don't have a practical way to register horses with multiple color factors.