Color temperature is a measurement used to describe the relative color of white light. A warm white light can look golden or amber, while a cool white light can appear almost blue.
Color temperature is measured in degrees Kelvin (K). Higher numbers on the Kelvin scale correspond to cooler colors, while lower numbers on the scale correspond to warmer colors. Although that might seem backwards for a temperature scale, we use the terms “warm” and “cool” because we so strongly associate amber, yellow, and orange with warmth and blue with the cold. Trust your associations, and not the number of degrees, when talking about warm and cool colors!
Direct sunlight has a color temperature of around 5800 K. General daylight (especially on a cloudy day) is cooler, with a color temperature of around 6500 K. Standard incandescent bulbs have a warmer look, and therefore a lower temperature of around 2400 K.
Warmer color temperatures are thought to be more relaxing and appear more flattering to skin tones, while cooler color temperatures promote concentration and are better for visual tasks such as reading.