The one thing I do not like about Grey Knights. Its one chapter. No other chapters are really supposed to exist, which means that you can either create your own and say they do have chapters derived from themselves (an even greater secret than their existence), or work in one paint scheme.
I decided to keep it pretty standard.
Overall, I have 40 purifiers to finish, which I have a good jump on. 4 Rhinos, and 5 Dreadnaughts are next. Then its just a few minor misc models here and there, which includes Crowe, a Grand Master, and some more Psykers.