No red! Red on chestnuts is not a good look or combo. Stick to forest green or just black and white. One color I noticed that popped is french blue. Contrast orangey coats with blues and redder coats with greens. Also, black and white does not mean boring when it comes to chestnuts. Play around with the piping around a black or white saddle pad. Adding a little (emphasis on little) silver for a zest of excitement can also work.