We ride with a set of sleigh bells and wear bright colors. We ride in pairs and chat ... not too many deer carry on conversations ....
I buy left over Halloween hair color spray, you can get orange, pink, purple..pretty much all colors, and color my horse. No chance of a rainbow deer!
It's a good idea to protect your dogs too. I always take my dogs with me when I go out with my horses. They wear brightly coloured racing vests so they don't get mistaken for deer.