It's measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000 ... encompasses cloudy days and bright blue skies. Light bulb color temperatures typically fall between 2,500K and 6,500K.

These bulbs are higher on the Kelvin scale, registering between ... but cool or bright white light bulbs specifically refer to color temperatures between 4,000 and 5,000 Kelvin.