How come they wear only white and grey pants for baseball and not other colors

Question

How come they wear only white and grey pants for baseball and not other colors

Answer 1

Lots of teams had different colored uniforms for years. The Indians had full blue and red uniforms. The Giants had orange uniforms as did the Orioles. The Pirates had full yellow (gold) and black unis. The White Sox had full blue uniforms. But most teams thankfully abandoned those get-ups in favor of road gray uniforms and the occasional light blue jersey. It looks a lot better and I'm sure the warm summer sun and darker colors absorbing the sun probably had something to do with it.  

Answer 2

Some teams have worn other colors.  The Pirates back in the 70's wore yellow pants and black pants.

I think the main reason is dark clothes absorb the heat and light reflects it.