Diamonds are graded on a color scale established by the Gemological Institute of America (GIA). The grade ranges from D (colorless) to Z (heavily tinted). Truly colorless diamonds, graded D, are treasured for their rarity. Color differences are so subtle that only a highly skilled professional will detect any color in E or F stones. Even when a stone has a visible tint, such as K or above, it can still be very lovely if it has good clarity and cut. Warmer colored diamonds (K–Z) are particularly desirable when set in yellow gold. Icy winter whites (D–J) look stunning set in white gold or platinum.
Nature has also created diamonds in intense shades of blue, green, yellow, orange and pink — and red, which is rarest. These diamonds are called colored fancies, and the more intense the color, the greater their value.