1. Any color photon carries some energy. If it's absorbed in some material it will generally heat the material up.
2. Since all the colors carry energy, they can all burn your skin
if enough light is absorbed. That applies to visible light as well as
infrared and ultraviolet. However, you can see visible light so you're
not likely to be surprised by whatever damage it does. The ultraviolet
not only dumps heat into your skin but also triggers some specific
chemical changes that can be dangerous, especially by breaking DNA
molecules. Cancer is one common result of ultraviolet skin damage.
"Sunburn' usually refers to some aspects of this chemical damage, not
to the simple heating produced by lower-frequency light.
While all colors of light carry energy, people who design lighting
for movies, television, interior decorating, cars, etc. do speak of
"warm" and "cold" colors. These names have absolutely nothing to do
with the amount of energy carried by the photons or their ability to
burn skin (or eyes). They have something to do with our perception of
what warm and cold objects look like when we encounter them in our
environment. Objects that are hot will glow red. The hotter they get,
the more white or even blue they will glow, because blue light carries
more energy per photon than red light. But most of us have rarely, if
ever, seen anything that's so hot it glows blue (except for some
stars), so most of us think that red things are hot. Blue and white are
called "cold" colors by interior decorators and by the people who
arrange the lights on movie sets because those are the dominant colors
we see when we go out on a clear, snowy day. Blue is also the color
people's lips turn when they get cold (and whole faces if they are
really really cold).
(republished on 07/27/06)