White light can be produced by mixing differently colored light, the most common method is to use red, green and blue (RGB).
Hence the method is called multi-colored white LEDs (sometimes referred to as RGB LEDs). Because its mechanism is involved
with electro-optical devices to control the blending and diffusion of different colors, this approach is little used to produce white
lighting. Nevertheless this method is particularly interesting in many applications because of the flexibilityof mixing different colors,
 and, in principle,this mechanism also has higher quantum efficiency in producing white.
There are several types of multi-colored white LEDs: di-, tri-, and tetrachromatic white LEDs. Several key factors that play among these different approaches include color stability, color rendering capability, and luminous efficacy. Often higher efficiency will mean lower color rendering, presenting a trade off between the luminous efficiency and color rendering. For example, the dichromatic white LEDs have the best luminous efficacy (120 lm/W), but the lowest color rendering capability. Conversely, although tetrachromatic white LEDs have excellent color rendering capability, they often have poor luminous efficiency. Trichromatic white LEDs are in between, having both good luminous efficacy (>70 lm/W) and fair color rendering capability.
What multi-color LEDs offer is not merely another solution of producing white light, but is a whole new technique of producing light of different colors. In principle, most perceivable colors can be produced by mixing different amounts of three primary colors, and this makes it possible to produce precise dynamic color control as well. As more effort is devoted to investigating this technique, multi-color LEDs should have profound influence on the fundamental method which we use to produce and control light color. However, before this type of LED can truly play a role on the market, several technical problems need to be solved. These certainly include that this type of LED’s emission power decays exponentially with increasing temperature, resulting in a substantial change in color stability. Such problems are not acceptable for industrial usage. Therefore, many new package designs aimed at solving this problem have been proposed and their results are now being reproduced by researchers and scientists.