Determination of the color characteristics of a diamond implies visually estimating the primary and the secondary color (or tone), and the color saturation. To determine these characteristics, a gemological daylight lamp and a white paper sheet are used. The latter serves as a background.

   On the basis of their color, diamonds tested for natural/synthetic origin can be ranked among the following groups:

• Yellow, yellow-green, green, yellow-brown, brown, as well as red and red-tone diamonds;
• Colorless and almost colorless diamonds;
• Cyan and blue diamonds.

Color characteristics of natural and synthetic diamonds

• Yellow diamonds.
  Both natural and synthetic diamonds can be yellow. As a rule, synthetic diamonds are yellow, yellow-brown, or brown.
  Yellow color of synthetic diamonds is usually well saturated. Those diamonds weakly yellow-colored are natural, as a rule.
  Both natural and synthetic diamonds may acquire intense yellow color (including some additional tones) as a result of treatment, that is, artificial change of color. Additional orange and brown tones are typical of natural stones, while greenish tones are peculiar to synthetics. Treated diamonds having colors from pink to dark red are rarely found. Such stones can be both natural and synthetic.
• Colorless and almost colorless diamonds.
  Colorless or almost colorless diamonds can be found among both natural and synthetic diamonds.
  Jewelry-quality synthetic diamonds, which are colorless or almost colorless, are rare. Such diamonds show characteristic phosphorescence: they emit blue light after being exposed to S.W. ultraviolet light.
• Cyan and blue diamonds.
  Blue samples can be found among both natural and synthetic diamonds.
  Some synthetic blue/cyan diamonds sometimes have additional greenish tone.
• Diamonds of other colors.
  If the color characteristics of the sample under study match none of the above-mentioned groups, its origin is most likely natural. However, additional tests are needed to confirm this conclusion.