if you are talking about the red, green and blue bulbs in a projection tv, all you need to do is take the back cover off and change the bulbs. bulbs, not bulb. you are wasting your time and money if you only change 1 of them. a little advice first. wipe the bulbs off with a slightly damp cloth . do this when the tv has been off for awhile. wipe with dry cloth to make sure there is not any moisture on them. you will be amazed at how much dust can accumulate on these bulbs. bulbs are around $125 each. you may be a lot better off using that money towards a new and much better tv.