As they stopped to pick up Ian Malcolm in Dallas, Ellie Sattler questioned him about his choice of clothing given the hot and humid weather of the state. Malcolm responded that black was actually the best color to wear for the heat. He explained that Black Body radiation helped block the heat, making sure he was at a uniform temperature. Black Body radiation is a type of electromagnetic radiation within/surrounding a body in thermodynamic equilibrium with it’s environment. Thus by wearing only black or grey clothes, Malcolm had achieved this state of balance, and his clothes absorbed the radiation, and thus the heat.
Jurassic Park by Michael Crichton page 72 (First Edition, Thirty Fourth printing)