A specification of the apparent color of a light source relative to the color appearance of a reference source, measured in kelvin (K). The CCT rating for a lamp is a general indication of the "warmth" or "coolness" of its color. Lamps with a CCT below 3200 K are usually considered warm (more yellow) sources, whereas those with a CCT above 4000 K are usually considered cool (more blue) in appearance.
Many sources do not have the same characteristics as black body radiators. However, sources that have a mainly white light output can be given a correlated color temperature. This is defined as that temperature of the black body radiator that most closely matches that of the light source.
The perceived color of light expressed in Kelvin (K)