The guys at DipYourCar did a fun experiment where they put five coats of black-to-clear thermochromic paint on a lime green car, then tossed hot water on the hood. Worked better than they expected, as they had never tried it before! They missed a chance to sit naked on the hood, though.
Before you run out and do this with your car, know that the thermochromic effect diminishes over time as the paint is exposed to sun and heat.
Image: YouTube / DipYourCar