While diamonds often appear colorless, they may actually contain subtle yellow or brown tones that will affect their value. The closer a diamond is to colorless the more valuable it becomes. Diamonds with no hint of color are very rare. Diamond color grades start at D (colorless) and continue through Z (light yellow/brown).
Diamonds having vivid "fancy" colors - reds, blues, pinks and bright yellows - are extremely rare and highly prized.