We tend to think of midday sunlight as the standard for pure white light. However when daylight is passed through a prism, the visible light is actually rendered as equal parts of a continuous spectrum. This spectrum is taught to schoolchildren by the name ROY G. BIV. Each letter standing for the visible colors produced by white light in the order it appears across the spectrum, Red, Orange Yellow, Green, Blue, Indigo, and Violet. In contrast, artificial light sources give off varying amounts of these colors. Incandescent light includes most of the spectrum but has a large proportion of red and yellow. When dimmed, incandescent light will become more orange in color. Many people think of fluorescent light as being high in green and blue, but today fluorescent bulbs come in over 200 colors.
Halogen lights produce a brighter, “whiter” light, than both standard incandescent and fluorescent light sources. Because of this brighter, white light, halogens have become very popular for both commercial and residential lighting.
Color temperatures as measured in degrees Kelvin (K) are used to formally rate light bulbs. Temperatures below 3,500 degrees K are warm-toned, more yellow in color; while higher temperatures are increasingly cool, or blue in color.
| Color Temperatures | ||
| Approximate | | Light |
| 6300° | | Daylight Fluorescent |
| 5500° | | Natural Summer Sunlight |
| 4100° | | Deluxe Cool Fluorescent |
| 3000° | | Deluxe Warm White Fluorescent |
| 2900° | | Quartz Halogen |
| 2800° | | 100 Watt Incandescent |
| 2600° | | “Incandescent” Fluorescent |
| 2500° | | 40 Watt Incandescent |
| 1800° | | Candlelight |
