@Caine22 Look up pictures of dragons done by good artists - Horiyoshi 3, Shige, Leu, Mick...many more...
Determine what you like and take examples to your tattooer. He should be able to help from there. If he or she needs more than that, chances are you have the wrong artist for the job. Just my opinion...color can be very subjective and can be limited to what has already been done to the piece. (You likely won't be getting very vibrant colors in areas already shaded dark) However, an artist with experience doing this style will likely have a few classic color schemes that would work.