In Jurassic Park, Dr. Ian Malcolm says he wears black to stay cool even in warm or hot climates. Is there truth to his claim, is it cinematic fiction, or character development?
It is true under certain circumstances anyway (e.g. air is not still). This is really a question for Physics.SE, not SciFi, but here's a link with more info.
In brief, in sunlight, black absorbs more of the light, so it doesn't get through to you; if the material is fluffy, then the outside layer absorbs all the heat and is cooled by the wind; inner layers are dark and cool. Also, the hot air rising on the outside can create air currents that are strong enough to help cool you underneath the clothes if they're loose enough. (Air currents are extremely important for keeping cool, since humans sweat, and evaporation is a major source of cooling.)
Incidentally, it does not appear to me that Dr. Ian Malcolm as shown in the movies is wearing clothing that optimizes his ability to stay thermodynamically cool. Rather, the clothing appears to be chosen for him to stay socially cool.
This is fiction. Wearing black actually heats you up, wearing white will cool you down.
It has to do with colors and light. Light works on an RGB model, or additive model, which means you start at white and add to get to black. How pigments work are the same, if all the pigments are off, you've got white, if they're all on, you've got black.
Pigments that are on take in the colors you're not seeing, in the case of blue, red light and green light are being absorbed and blue light is being reflected. When you have white objects, because all of the pigments are off, red, green and blue light is being reflected. The opposite is true with black, red, green and blue light is absorbed by the object, making it hotter.
Black bodies radiate away heat when in shade. Dr. Malcolm intended to be in shade.