Color Thermal Radiation and Absorption

Black is the best absorber and emitter of light and heat. Therefore wearing a blacks shirt is said to keep you cooler in the summer as the black shirt will absorb and emitt all light emitted from the sun while absorbing heat emitted from your body within the shirt (cooling you off). Another example is the SR71 black bird is black to help absorb internal heat while emitting that heat away from the plane, keeping the plane cooler. 

Whit colors are good at reflecting light. Wearing a white shirt would reflect light emitted from the sun but theoretically "cook" you from the inside as the heat emitted from you body will be reflected back onto your skin.

This being said, why is it that black cars are hotter than white cars in the summer? Shouldn't the black color absorb and radiate more heat than the white car keeping the car cooler according to the shirt and black bird theory?

Cheers

Nope.  You’re not wearing the car. 

Hot surface will radiate heat in as well.  Black seats even worse. 

Been a while but I seem to recall it is something like this...

A Black body absorbs incoming radiation, raising its temperature. It will re-radiate (at a rate proportional to its own temperature raised to a fourth power - I think) but it’s net radiation will be negative until it gets hot enough to balance the absorbed heat and lost heat from re-radiation.

A perfectly reflective body (is this white?) does not absorb any radiative heat and so does not raise its temperature.