One of the 4 c's (Color, Cut, Clarity, and Carat Weight), Color is surely one of the first things you'll learn about when looking to buy a diamond. Simply put, here's how it works.
The GIA color scale extends from D to Z with D being colorless and Z being light yellow or brown.
Many people think of gem quality diamonds as being colorless, however truly colorless diamonds are extremely rare. Most diamonds used in jewelry are nearly colorless with tints of yellow or brown. These tints of color present in diamonds that fall in the near colorless range (G through J) are very difficult to detect with the naked eye under normal lighting conditions.
Yellow or Brown diamonds that exhibit more color than a Z color diamond are classified as "fancy" colored diamonds.