From experience people in the know paint cages black, Just for the fact that if you chip scrape or dent the cage with helmets straps ect.. its easy to touch in the damage with a pot of paint and a small paint brush.
But then again are you going to be giving the car any abuse. If not then go for red. Only thing is it will cost a hell of a lot more to paint it in red for the fact the fact of all the masking.
If you go for red you will have sharp joins where the red meets the black normally you just paint the tubes red and the plates/ mounts body colour.
__________________
|