The colour temperature of light bulbs is measured in degrees Kelvin and designated by K. The lower the degrees Kelvin, the more yellow the light, whereas the higher the degrees Kelvin, the more blueish the light.

The light emitted by bulbs tends to be different: yellow, white or bluish. The warm white light is in the range from 2,700 to 3,200 K, white light – from 3,200 to 4,000 K, bluish white light is more than 4,000 K and bluish light is over 6 000 K.

More yellow light is advisable for living space, while white light is suitable for workrooms and corridors.