What do you look for when buying colored gems?
It is not nearly so easy as when looking to buy a diamond. There is no universally accepted grading standard for dealers to adhere to and there are the frustrations that come from finding that one dealer's "nearly flawless" looks like another dealer's "moderately included".
As if what you found in the clarity column were not confusing enough, how do you translate "daffodil yellow" or "sky blue" let alone "rich royal purple with hints of velvety blue"?
Oh, and forget about cut grades! There is no standard for cutting, nor can there be. Each stone has its own refractive index, which determines how the light will play throughout the stone. This means that angles that will create an incredible looking tanzanite might create a lifeless looking amethyst.
The GIA in its efforts to at least give us some guidelines in colored stone grading and classification has gone to great lengths to provide us with a workable system that is at best a good beginning.
Personally, I feel that there will never be a totally accurate system for describing colored gems. Even photography does not provide us with an accurate system to share the beauty of some colored stones, as the chemicals in the stone cause light to react unfavorably, creating an unattractive looking stone where there is great beauty in real life.
I once spent hundreds of dollars with a photographer trying to get a good picture on an incredible chrome tourmaline. Its magnificent rich green color always came out an unattractive brownish yellowish reddish yuck color on film because of the chrome in the stone.
Here are some basic guidelines that you can use in your search, but remember, to paraphrase Mr. Gump, "Beauty is as beauty does!" Look at all the certs you want, but buy the stone because it is beautiful and makes your heart sing. If it does not, don't buy it!