A colorized coin is a coin that has any sort of artificial coloration applied to it, whether done by an official coin-making institution, such as the Royal Mint, or unofficially by other enterprises and artists. Such an act is usually performed by intentionally gluing or fusing a decal or sticker to a coin or painting a coin with acrylic or enamel paint. Colorized coins made by official mints are legitimate collectibles and do hold numismatic value, whereas their unofficially colorized counterparts are deemed numismatically worthless by collectors.
A number of unofficial dealers sell colorized United States coins online. Even though the coins themselves were struck by the United States Mint, the colorization was likely done by a private enterprise or artist. There is no law that prohibits the practice of colorizing coins in the United States, as long as the coins do not violate U.S. trademark and advertising laws if intended to be sold.