1. NEVER share lenses with anyone else. This allows microscopic organisms to transfer between the wearers and serious eye problems can result.
2. Never buy your color contacts from flea markets or beauty salons. The lenses you obtain from these places are of questionable quality and can be made from materials that are dangerous to your eyes. According to the FDA, contact lenses are medical devices and can only be sold by an optometrist or licensed contact lens retailer.
3. If you have 20/20 vision and want to wear color contacts just for fun, visiting a doctor is highly advisable. Most colored lenses offer two or more options for a base curve, a parameter that needs to be established by a doctor to ensure a proper fit.