The answer to the black clothes in the sun "myth" is that it depends.
The study referenced from the 80s was looking at specific clothing worn by Bedouins in the desert, who indeed wore/wear black clothes in intense heat. The physics of it was that they wear VERY loose fitting robes, made of very thick black materials. (Note the study affirmed that black material gets hotter, faster--so what was going on?)
The very thick material meant that the heat buildup on the material reached the skin/body slower. The very loose robes, combined with the heat buildup on the black robe, creates an upward daft beneath the robe that cools the body.
So, if you want to wear thick, heavy robes on the baseball field, it may work. But if you want to wear pants, belts and jerseys, you'll do better with lighter clothes, since dark material actually does absorb more heat, the thin material will translate it to your skin faster, and the tight fit will disallow the cooling effects.
