Welcome to the forums Leon
As tescoapp says, colour blindness will not prevent you from obtaining a JAA Class II medical (ie the one you need for a JAA PPL), but it will be claused for daytime flying only, unless you can pass a lantern test. (The lantern test requires identification of a series of moving red, green, and white lights)
Details can be found on the CAA's website
here
Good luck with your ppl training, feel free to ask questions on here, but don't forget to check any provided advice with your instructor!