There are four types of colored contact lenses: visibility tints, enhancement tints, opaque color tints and light-filtering tints. Many of these colored contact lenses are available in plano form (without visual correction), as well as in designs for people who have astigmatism, who need bifocal correction, or who want a disposable or frequent replacement lens.

A visibility tint is usually a light blue or green tint added to a lens, solely to help you see it better during insertion and removal — or if you drop it. Since it's a very light tint, it does not affect eye color.

An enhancement tint is a solid (but translucent) tint that's a bit darker than a visibility tint and does affect eye color. As the name implies, it's meant to enhance the existing color of your eyes. These types of tints are usually best used by people who have light colored eyes and want to make their eye color more intense.

Color tints are deeper, opaque tints that can dramatically change your eye color. They are usually are made of patterns of solid colors. If you're tired of batting a pair of baby blues or not interested in hearing yet another rendition of "Brown-Eyed Girl" crooned your way, you can change your eye color with these tints — at least temporarily. Color contacts come in a wide variety of colors, including hazel, green, blue, violet, amethyst and gray.

The companies that make colored contact lenses have gone all out to mimic the natural look of the colored portion of the eye. Since this area is made up of a series of colorful shapes and lines, some color contacts feature a series of tiny colored dots on the lens to make it look more natural on the eye. The center of the lens, the part over your pupil, is clear so you can see.

Costume or theatrical lenses also fall into the category of opaque color contact lenses. Long used in the movies for special eye effects, these lenses are now widely available for novelty use and can temporarily transform the wearer into an alien or cheetah, among others.

Light-filtering tints are a more recent development. These contact lenses are designed for sports use, because they enhance certain colors (such as optic yellow, the color of tennis balls and some softballs and golf balls), as a result of muting other colors. The result is that the ball stands out against the background and is easier to target. The lenses can also be used by spectators.

One type of contact lens has been developed especially for golfers, so they can better distinguish between the various greens on a golf course. Amber-tinted ones are coming in the summer of 2005; called MaxSight, they are being worn by some professional baseball players, who find that they help filter out the blue light that reduces their ability to see the baseball clearly. (MaxSight will also be available in green-gray, which is better for golfers.)