The color temperature of a light source is defined by its colored comparing within the visible spectrum of light issue a "black body" heated to different temperatures. For this reason this "color temperature" is expressed in Kelvin, although not exactly to temperature measurement, to be the same only a relative measure. As a black body gets hotter, wave length of light emits progress through a sequence of colors from red to blue.
Basically we want to know if we must use cold light (> 5000K) or warm light (<3000) Depending on usage and the environment in which they are to be used. For colors based on black body theory, blue occurs at higher temperatures, while red occurs at lower temperatures. This is the opposite of the cultural associations attributed to colors, in which “red” is “hot”, and “blue” is “cold”. As temperature decreases the color is red and as we increase the temperature, the color tends to white. The middle is pure white (6500K approximately).