LOL, don't decide what color to put your horse in based on a couple of people calling it by the wrong gender.
To some people, all animals are either "him"s or "her"s, regardless of their gender. I know some folks that call all animals "her" even after they find out it's a boy. Annoys the heck out of me, but what can you do? LOL
Warm colored horses always look good in cool colored tack. So, chestnuts look good in blues, greens, purples, grays. Some chestnut horses can pull off reds/oranges/yellows, but IMHO, they are relatively rare and you have to find just the right shade.