As others have said please post more, but because your issue seems similar to one I had before I will hazard a guess.
RGB LEDs use three different segments that mix to make various colors. They are not however, perfectly balanced so if you turn all of the segments on equally, red will almost always overpower the other two colors and you end up with a red light. Try using PWM (analog writes) to balance the three segments until you get an acceptably white shade. Having done this myself I can say for certain that getting a good white out of a RGB LED is not easy and will require a good deal of time and patience.
All of this said, it could be that you are missing the other two segments entirely. If that is the case you will need to post more so we can check your wiring.