I know black conducts heat while white reflects it.

But they are colors after all.

If a metal is painted black, it conducts more heat or at a rapid speed than it would do before it was coated.

But, AFAIK, colors don't have any special "substance" in them, which might trigger the sudden absorption of heat or reflection of the same.

What is the physics behind this? Are colors by themselves, some catalyst kinda thing?