Color
A diamond’s body color (from colorless to yellow) is determined by the Gemological Institute of America’s color scale.  Like the other four Cs, color is a matter of preference.  Some people insist on colorless diamonds for their breathtaking purity and radiance, while others prefer slightly yellow diamonds for a warmer look.

What causes different diamond colors?  The answer is chemistry.  A diamond is made up of pure carbon.  During its development, other natural elements may be incorporated into the carbon, causing a chemical reaction that changes the color.  For instance, traces of nitrogen cause yellow diamonds, while boron gives diamonds a blue color.

Over time, diamonds will never change color, but a diamond's setting can often influence its appearance.  A yellow gold setting makes a light yellow diamond appear whiter.  Platinum and white gold settings, however, may make the yellow hue in a diamond more apparent.  Similarly, a colorless diamond set in yellow gold may reflect the setting's yellow tint.

Fancy color diamonds fall into the Z+ category.  These diamonds include colors such as yellow, blue, violet, orange, pink and red - the most rare.  Diamonds of this type are very unusual and therefore highly valued.  One of the most famous fancy color diamonds is The Hope Diamond, displayed in the Smithsonian Institution in Washington D.C.  The Hope Diamond, though not the largest diamond at 45.52 carats, is well known for its dark blue color.