strout-
the color temperature of a bulb refers to the black body radiation temperature in deg kelvin. a back body refers to a perfect radiator so the black body specturm is the wavelength (color) distribution of the photons (light) comming from the radiator at a given temperature. it is important to know the temperature of a bulb is actually the manufactures subjective approximation of what black body spectrum their bulbs output is similar to combined with a little marketing for good measure. this is why a 20k (20,000 deg kelvin) bulb is usually more blue that a 10k bulb, but two 20k's from different companies will look different.
-bart