A gem stone or birthstone can be many colors. Generally speaking, the deeper the color the more valuable the stone.

Gems come in every color of the spectrum. While sapphires, rubies and emeralds are what come to mind first when one thinks of a colored gem, there are so many other beautiful colored gemstones to consider. Even among gems normally associated with one color, there are gradations and variations to them. A sapphire, for example, comes in many different hues of blue, depending on where it's from. But sapphires can also come in pink, yellow and green.

The most highly prized colored gems are in the very deepest, richest hues of the color. While sapphires can range from pale blue to near-black, the most valuable are a rich, deep blue. The same holds true for rubies. While they too can range in color from pale to very dark and murky, the most highly-valued color is what's called pigeon's blood, a deep blood-red ruby that is mined in what was once known as Burma.

The most expensive emeralds are a deep green, although emeralds themselves come in a broad spectrum of hues, from yellow-green to blue-green. All colored gems, and clear gems, depend on expert cutting and polishing to showcase the colors in all their subtleties and brilliance.

Generally the deeper and richer the color, the more valuable the stone. The best amethysts will be a dark, royal purple. A lighter-colored amethyst simply isn't as valuable.

But many people prefer these lighter or darker gradations in color. And, they tend to be more affordable. A slightly lighter-colored amethyst is much easier to obtain than the "ideal" color, but is still a beautiful gemstone.

Oddly enough, diamonds are rated by how colorless they are. The less color, the higher the grade of diamond. Unless of course it's a defined color such as a pink diamond or a canary diamond. These are almost as highly prized as a near-colorless diamond.