The color grades shown next to each Asha shape and size are their colors on the GIA Diamond color scale. We have the Ashas reviewed and color graded after the coating run, and they are graded the same as natural diamonds.
While most people think of all diamonds as simply being white or colorless, the reality is that most gem grade diamonds have varying levels of very light tinting (typically yellow). Thus, they are accorded different color grades ranging from pure colorlessness (D) down to (Z).
This photo from the GIA labs may help - a series of diamonds arranged in descending color. Note how the tint slowly increases (leftmost are the D/E/F grades):
About the GIA diamond color scale:
"The Gemological Institute of America (GIA) uses a "D" to "Z" scale it developed for grading the color of "white" (non-fancy colored) diamonds, where "D" is colorless and "Z" is yellow:
- colorless: D, E, F
- near colorless: G, H, I, J
- faint yellow or brown: K, L, M
- very light yellow or brown: N, O, P, Q, R
- light yellow or brown: S, T, U, V, W, X, Y, Z
Diamonds that rate toward the colorless end of the range are sometimes known as "high-color" diamonds, and those toward the other end, "low-color" diamonds. These terms refer to the relative desirability (as demonstrated by market prices) of color grades, not the intensity of the color itself.
Diamond color is graded by comparing a sample stone to a master set of diamonds with colors defined as "D" through "Z"."(from Wikipedia*)
Thus, if you are unclear about colors, you can certainly visit a local jeweler and ask to see a natural diamond in the same color grade (or grades) to see how different colors look. Optionally, a quick search on the web under 'diamond color grades' will probably generate some good photos and comparative color charts as well.
We should note that color grade differences are very fine, and that is why diamonds have to be graded loose and against a white background (its a lot harder to see the color grade difference once mounted into a piece of jewelry). There is not a huge difference between an E color and an H color, but it is there.
The general consensus from our customers is that the E/F colors are icy in appearance, and the H colors have just a hint of steeliness.
*Diamond color. (2006, July 4). In Wikipedia, The Free Encyclopedia. Retrieved 21:28, September 9, 2006, from http://en.wikipedia.org/w/index.php?title=Diamond_color&oldid=61972868