I'm working on a set in Photoshop CS6, and for some reason it's only allowing me to use black, grey, and white, and I'm not sure how to fix :C Please help. PM if you know how please

This isn't a Discussion topic - don't post threads like this in the Discussion board.

Moved to Rapid Threads. Maybe someone here can help you.

go to image(localized in the top bar)
click mode and see if you have RGB color selected

Well, did you try to select from the Colorwheel? Perhaps your settings are set to some sort of Greyscale, and as a result it isn't allowing you to change colors. If I had my CS6 up I'd toy around and see for you.

Kratox is correct, you go to Image(at the top) > modes> and change to RGB although I personally use CMYK