How well do you know the 4 C's of diamond ring shopping?

Last week, we began looking more closely at these diamond-buying guidelines, starting with diamond cut. Today, let's continue with the second important characteristic: diamond color.

When we talk about the color of a diamond, we're actually referring to the lack of color. The most valuable diamonds are absolutely colorless - and also extremely rare.

The Gemological Institute of America (GIA) has established a diamond color scale that ranges from D (the highest grade; colorless) to Z (a pale yellow color). A diamond with a stronger color will fall closer to Z on the color scale.

Photo: "How to buy a Diamond" - GIA

This color spectrum is very subtle and often impossible to detect as an untrained observer. When determining the color of diamonds, gemologists use a plain white background and controlled lighting to compare new stones to diamonds that have already been categorized by color.

Once a diamond is set in a ring and viewed in normal conditions, it is much more difficult for the eye to see color differences. The stone is no longer placed next to another diamond for comparison on a white background; instead, it is set into a ring and worn in everyday settings. For this reason, the H or I diamonds featured in your wedding trio set may look perfectly colorless when you wear them.

Some diamond fanatics want purity of color over all else and are willing to spend top dollar for diamonds with a grade of D to F. But most couples shopping for an engagement ring or a wedding trio set are more interested in finding quality at a good value. When you shop for diamonds with a color grade of G to I, you will find options with excellent value: they'll appear colorless or nearly colorless to the naked eye, but they are far more affordable than higher grade diamonds.

Color can also be easier to see in larger diamonds, so rings that feature many smaller stones instead of one large stone often appear to have a higher color grade.