An absolute temperature scale used in scientific circles.
The "color temperature" of a light source, monitor or image area, defined in "kelvin" (K), is the temperature a perfectly black radiating object would be if it glowed that shade of white. Average daylight is standardized at 6500 K (Europe) and 5000 K (North America). Higher temperatures are bluer, lower temperatures are redder.
Unlike other temperature scales, the term "degrees" is not used in relation to kelvin. So a temperature is "6000 kelvin" or "6000 K" rather than "6000 degrees kelvin".