You've been told that having a certificate or a diamond grading report is important, and as a responsible consumer, you get one - unfortunately, you probably won't understand a word of what is on that diamond grading report, unless you are a jeweler. On the color grading scale, D, E, and F mean that the diamond has no color. G, H, and I means that it has very little color. J, K, and L means that the diamond has a slight yellow color. P, Q, R, S, T, U, V, W, and X means that the diamond is a darker shade of yellow. Z means that the diamond has a fancy color - other than white or yellow. On the color grading scale, D is the most valuable, and X is the least valuable - however diamonds that get a Z rating are the rarest and most expensive diamonds in the world. There are many aspects to a grading report. Figuring it all out can be very confusing. You should talk to a jeweler you trust, and have them explain everything on the diamond grading report to you.  Allen Jesson writes for several sites that specialize in Antique Engagement Rings, Vintage Engagement Rings and A Gift Of Poetry