the idea is that black colour dissapates heat faster,
the concept stems from the below example
in desert nations, workers dress as to how often their in the shade
if your walking from shady spot to shady spot, and spending time in that shade
you wear dark colours, you get sweaty cause of the layers but in the shade
you cool faster as the wind blows through
likewise if your is the sun a lot you wear light coloured clothes to not absorb as much heat
and the wind blowing through your clothes evaporates the sweat and circulates a cooler air
about your body
but its the wind powerd evaporation that's doing the most of the cooling
at night your not dealing with solar radiant absorption, but keeping your body from absorbing heat
from the air or nearby warm objects
again wind and evaporation is going to be the major factor
so, yes a black shirt will shed heat faster than a white one, but in the instance of clothes
the difference is very minimal, perhaps unnoticable
now if you change the question to "will a steel body car..."
the metal of the black car should cool off faster in the shade/dark than a white car
at a noticable degree of diferance
but there's always the factor of airflow, cause if there's no airflow, the lingering warmth
means a slower/longer cooldown time