More specifically, it may not be so much a question of which is hotter or cooler, but how black or white allows heat equilibrium. Black color better allows the transmission of heat: heat flowing from a location of higher to lower temperature for equilibrium; while white conversely, is more resistive to the flow of heat, thus promoting a difference in temperature. That is why a black potbelly stove seems to radiate heat so well; but if one were to make that stove white, the stove may be hotter inside and the metal of the stove may be hot, while it would not seem to be as hot because less heat is radiating, or, flowing away from the source. If that stove continued to get hotter however, it may be expected that the function of heat being forced out would tend to turn that stove black: resistance breaks down. On a cold night, the same amount of heat would keep the inside of the white car warmer, while when It is hotter outside the white car will resist warming. Black both absorbs and radiates heat well, transmits that is, so whether the interior is black or white is also a factor in heat coming in from the outside. Maybe that is the social intimate feeling derived when people are dressed in black: body heat would be more sensed when two people in close proximity are wearing black.