I would think you would want to stay away from dark colors, even though everything will bleach to a gray from the sun with time. You are hot there already, no need to make it hotter with dark colors absorbing even more heat. A friend and I had lunch this summer at a restaurant this summer outside. It was 88F and sunny, and there were no more tables with umbrellas, so we sat in the sun. Our silverware got too hot to handle, and we had to move inside.
Just think about those poor plants, and you making it worse with a dark color!
