In order to answer the question I set a number of the samples with different paints on them on a foam insulation pad on the ground outside. Then I let them heat in the sun during the day and cool under a night sky.
I chose times when the weather was fairly clear. Then I measured the temperature at various times using a hand-held infrared thermometer. I kept track of the air temperature during the experiment.
During the day I measured sun elevation because the angle that the sun hits the samples determines how much light energy they receive.