Surprisingly, making a true LED in a white color is remarkable expensive, while red, yellow, blue, and green are achieved much more easily. As a work-around, we can use a combination of red, yellow, and blue LEDs to create almost any color, including white. Of course, this means that three diodes would need to be used instead of one, and therefore can be less efficient and more costly. A second option in making a white LED is to use phosphors, much like a fluorescent bulb. This allows the use of one diode, and is preferable to the first option.
There is so much flexibility in using color with LED bulbs. The same bulb in a given fixture can be programmed, for instance, to change to several different colors over time, producing an interesting and beautiful effect that bars, restaurants, or landscape designers may choose to use. City lighting systems like certain traffic signals can show messages in different colors depending on importance, severity, etc. Theaters and casinos can use multi-colored LED light bulbs on marquees and signs to attract passersby and to showcase upcoming specials or attractions. The possibilities are endless, thanks to the flexibility of LED light bulbs.