I would prefer to stick with lighter colors, because they deflect the sunlight and don't get as hot on sunny days. I've had dark colored cars in the past that were unbearable on hot days. The worst was an all black 1990 Mustang, with and all black leather interior. You could practically feel your skin ripping off of you when you tried to get in and out of that car in the summer. I think white cars tend to look cleaner too, even when they are a bit dirty. There is more contrast between the white paint and the tinted windows and trip so the overall higher contrast makes them look nicer.
The only bad thing is if you start getting some rust spots, because those are very very noticeable on white paint. But then again, a simple white paint job is easier to do, than, say a "metallic" paint job which is done in multiple coats and takes longer to do. Not to mention it is more expensive.