There is no absolute answer as to the grade at which color starts to show. It depends on whether you look at the stone from the side or from the top, what it is next to, what the lighting is like, etc. The best thing to do is to go to a jeweler, ask to see stones of various colors, and see what your preference is, given the price differences. It is best if you can find a jeweler that will let you take the stones outside so you can see them in natural light.