Most natural diamonds contain small quantities of nitrogen atoms that displacing the carbon atoms within the crystal's lattice structure. These nitrogen impurities are evenly dispersed throughout the stone, absorbing some of the blue spectrum, thereby making the diamond appear yellow. The higher the amount of nitrogen atoms, the yellower the stone will appear.
In determining the color rating of a diamond, the Gemological Institute of America uses a scale of "D" to "Z" in which "D" is totally colorless and "Z" is yellow.
Diamond Color Designations
* D, E, F - colorless (white)
* G, H, I, J - near colorless
* K, L, M - faint yellow or brown
* N, O, P, Q, R - very light yellow or brown
* S, T, U, V, W, X, Y, Z - light yellow or brown