I just spent some time playing with a fun tool to design your horse's color scheme. Now, it's not comprehensive, and the interface is a little clunky, but it is a marvelous time waster. (The things you are reduced to doing when you are being dumped on by a foot of snow...)
Here's what Tristan currently looks like to go XC.
I did one for Hannah's Tucker, too, except it needs more spangles.
Now, if you'll excuse me, I should probably duck and run...