I used to ride a very kicky little mare as a kid and i always diligently tied a big fat red ribbon around her tail AND braided one into her forelock. Kids still used to use her bum as a buffer when they couldn't stop tho, was as if the red called them to her rather than kept them away!!! Shows should include the colour warning on their entry forms IMO!!
Have used green with Beau as a baby but so many people asked me what it was for I gave up!! Not tried blue, might if I ever sell anything tho, at least people asking gives you opportunity to tell them horse is for sale!!!
I use a red ribbon for my mare - she doesn't kick but it certainly makes sure people give us a nice berth instead of running into us every five minutes