Light bulb colour is represented by the temperature. This is measured in a unit called a “Kelvin” or “K.” Kelvin itself starts at the lowest temperature possible: absolute zero and proceeds up for there. For example 72° F or 22° C is 295° K. The freezing temperature of water is 273° K.
Bulbs climb in temperature from a yellow glow at 2700K up to warm halogens at 3000K and upwards to bright white fluorescence at 5000K.

Picking The Right Bulb For the Room and The Role

The hue of a bulb closely matches the role it is intended for. An intimate dining room may have the cool yellow colour an Edison bulb. A commercial setting where light is needed for procedures may use a 4000K or 5000K bulb. Lighting does so much to set the mood. On the cool end of the spectrum, it can remind us dusk and campfires. On the high end, it can convey efficiency and order. While the spectrum is broad, our lighting choice stay in the 2400K to 5000K range.

Temperature Source
1700 K Match flame, low pressure sodium lamps (LPS/SOX)
1850 K Candle flame, sunset/sunrise
2400 K Standard incandescent lamps
2550 K Soft white incandescent lamps
2700 K “Soft white” compact fluorescent and LED lamps
3000 K Warm white compact fluorescent and LED lamps
3200 K Studio lamps, photofloods, etc.
3350 K Studio “CP” light
5000 K Horizon daylight
5000 K Tubular fluorescent lamps or cool white / daylight compact fluorescent lamps (CFL)
5500 – 6000 K Vertical daylight, electronic flash
6200 K Xenon short-arc lamp
6500 K Daylight, overcast
6500 – 9500 K LCD or CRT screen
15,000 – 27,000 K Clear blue poleward sky

Temperatures and Rooms They Fit

Less than 2000K: gives off a dim glow of light, similar to candlelight; best for low-light areas where ambient illumination is welcomed. Translation: dining room and hang space.

2000K-3000K: gives off a soft white glow, often yellow in appearance: living rooms, dining rooms, bedrooms and outdoor spaces. Translation: a relaxing space.

3100K-4500K: gives off a bright amount of white light: kitchens, offices, work spaces and vanities where task lighting is needed for working with cosmetics and clean spaces.

4600K-6500K: gives off a bright amount of blue-white light, similar to that of daylight; best for display areas and work environments where very bright illumination is needed. Translation: settings where you want to simulate daylight, as well as industrial and factory settings.