When talking about white light sources we use the description "warm" and "cool." White light with a yellowish tinge (think candlelight and fireplaces) is considered "warm." Incandescent lamps produce a warm white colour. Bluish white (think moonlight on cold snow) is considered "daylight." Fluorescent lamps can produce warm white or daylight (or anywhere in-between) depending on the mix of phosphors used.

It is important to remember that indoor spaces lit to lower light levels will typically look and feel better under warm lamps, while higher light levels are easier to tolerate using cool lighting. A space which receives an abundance of sunlight may seem more natural when cooler lamps are installed since their light is closer to high colour temperature of natural daylight.