Does it really matter what colour the flags are ? turn up pick your class pay your money then ride the flags you are told, it's not rocket science.
I rode M'bro 2 day at Fryup and there flag system worked well, I rode Eboracum and Thirsk last weekend and their system works ok, I know Guisborough use there own flag system and this weekend its a Scarborough trial and they are using a purple route for the first time for beginners.
I'm a beginner to the sport and I've managed to suss every club out so far, I say leave it as it is as it could cause mayhem to change to a universal system.