NO EXPERT HERE, but I have had the opportunity to see moissanite in person at several different stores on several different ocassions, and I was quite surprised at the obvious variations -- some of it was definitely more "colored" than others. Also, it seemed to me like the 1 carat sizes. Also, one of my co-workers has a moissanite pendant (probably about .4 - .5 carat?) and it really does look surprisingly a lot like a diamond.
There is a treatment that can be done to moissante that whitens them a dhade or two; however, I believe this voids the warranty on the stone from Charles & Colvard, but the warranty is for brilliance 9I believe) so it really seems not to matter. Ask your moissanite dealer about it. I know Bella Jewelry on eBay does this to thier moissanite stones if you request it.
THis is my set from Ebay seller BellaJewelryCompany.
It is heat treated and it does help toning down the yellowness and green tint that moissanite can show in the higher carat range. my moissanite is a 3CT round in a platinum Stuller Solstice. The band is a 2.75 CTW moissanite as well in 18KT white gold.
Charles and Colvard denies that heating a moissanite improves the color. I had a 2CT moissanite before I had this 3CT and the 2ct was more warm than the 3CT treated. If you want to draw your own conclusion, you should call him ( mario) and talk to him about the heat treatment. It worked for my moissanite. I am glad I got one that was heat treated.
Talking about the C&C warranty: It doesn't cover anything other than clouding. Not to much of a warranty if you want my opinion. Other sims offer a better warranty than this. Anyways... I love my moissanite. I want more!