Most diamonds can appear to be white to the naked eye, but in fact they can range from colorless to yellowish, with many gradations in between.
Colorless diamonds are the rarest and most valuable of all. A color grading scale is used to determine grades, due to there being many variations, this comes in very useful when used to categorize the shading differences from one diamond to the other. As the diamond increases with yellowness, it drops the value of the stone.
If a diamond is well cut, brilliance and dispersion can often disguise the coloration. As you may have seen or will find out, as you shop, many jewelers lack the expertise to accurately classify a diamonds color. Many others, regardless of their expertise, may be tempted to inflate the color value in order to inflate the cost. Protect yourself by asking to see the jewelers master color-graded diamond set.
As a further precaution, ask for the jewelers written assurance of the exact color grade. One of the best ways to guarantee the color of a diamond is to choose a jeweler who is competent and trustworthy. When doing this, make sure there is a title holder who has been accredited by the American Gem Society. They will be able to prove this either with a certificate or some other type of paper work stating their title. Always remember, you have to feel comfortable where you buy.