No matter what you do - someone will call your horse by the wrong gender! I had a guy at a state fair once ask if I would like to breed my mare to his stallion, which confused me as I only own a gelding! Just choose a color that you like and works well with your horse! I, personally, like to have two colors going for one horse so you can get mixed color pads, polos, etc. and it is more unique! Lucky for you it is easier to pick a good theme color for a solid color horse!
Either way - my vote is for purple!
Be dominant, not violent. Be assertive, not aggressive. Take in all the information you can get your hands on, but only give out what works, what is true, and/or what is genuinely useful - and only when asked.