How much money is saved over the lifetime for switching out a yellow light with an LED?
Considering that LEDs emit their energy in a narrow spectral band, it may seem surprising that White LEDs are available. There are presently 2 kinds of LEDs that have a visual white appearance. The earlier type actually consists of red, green, and blue LED chips packaged closely together. This kind of array can produce many colors, but with the appropriate currents in each chip, the combination appears white.
A newer kind of white LED consists of a blue LED combined with special phosphors that give off a broadband glow when excited by blue light.