I picked the all-red suit for my main driver.
For my B-spec squad, they all have the different suits with a kind of red on them (helmets especially, so we're matching in some way).
Most of my cars are in some shade of red (with a few odd ones and others not in that color to make my garage look less uniform and bland). I've taken a liking to Gran Turismo Red Metallic and Rosso Corsa. Wheels are usually black, but I'm not terribly picky. As long as it looks good on whatever color the car is.
Red just happens to be my favorite color, and it looks fierce.