For cars, I tend to be practical. It's almost always going to be white/silver/gray for me. Science has shown that white reflects a lot of light so it handles heat better. Silver/gray is close to white in handling heat, and tends to hide dirt better, so less frequent washes.

For clothes and a lot of other things, I prefer black or dark blue. I know white would be better for clothes for the same reason above, but I don't really like the color.