Sure they can! SBR Formula One (I love him, by the way) is a buckskin with the dun gene or "dunskin". Hollywood Dun It was too.Dun can affect any color it wants to.
This is the best way I've heard horses with multiple layers of color genes (like a dunskin):
"Think of it as adding food coloring to water. If you drop blue food coloring into water, what color will the water turn? Blue! But what if you add yellow color to the blue water? There's no law against adding a second modifying color to the blue water, so do it! It then changes to green. You can keep on adding colors, and the water will keep changing for a couple more turns."
Last edited by Poseidon; 10-15-2011 at 04:19 PM.