The four C's. A polished diamond's value increases according to its carat weight, colour, clarity and cut.
This combination is known in the diamond trade as "The 4 C's".
Diamonds come in many different colours ranging from "Blue
white", to black and from pink to orange blue or green. A diamond's
colour is considered by some to be its most important characteristic.
The most commonly traded stones are in the Blue white or D colour, to
Cape or K colour stones. The top colour of a diamond is known as the D
colour, followed by E, and then continues all the way through the alphabet
until Z, which is considered a fancy colour.