I'm not familiar with the lights, there's a myriad of manufacturers, and many have come and are already gone. I would be guessing, but I would say the W is for a White channel, B for the Blue, and M for Magenta. You'll have to do some trial and error with the intensity, depending on the type of coral you want, there's a big difference between 3' and 5.5".
My guess is your lights are moon light (m) and white (w) LEDs with B being for both? You should be able to figure out real quick by adjusting things and seeing what turns on. Also a picture would help a lot with iding the lights.