Did I not once hear that the polish--or lack of it--had slightly more effect on the radiation and absorption than the colour? So, matt black becomes the optimum for shedding heat from friction. Without specific figures, I would guess that this was far more important than the heat from the Sun being absorbed.
Having said this, try sitting on a dark green plastic chair v white at the side of pool on a hot day. Or simply ask a Saudi male and female for a comparison of their running temps.