"The Game Boy Color (ゲームボーイカラー, Gēmu Bōi Karā") is Nintendo's successor to the Game Boy and was released on October 21, 1998 in Japan, November 19, 1998 in North America, November 23, 1998 in Europe and November 27, 1998 in UK. It features a color screen and is slightly thicker and taller than the Game Boy Pocket. As with the original Game Boy, it has an 8-bit processor. The Game Boy and Game Boy Color combined have sold 118.69 million units worldwide."

Source: Wikipedia, "Game_Boy_Color", available under the CC-BY-SA License.

Region Locking:
Game Boy Color consoles are not region locked and games can be played on any system that reads standard Game Boy Color cartridges.

Compatibility
Game Boy Color consoles can play standard Game Boy cartridges.
Black Game Boy Color Cartridges can play on Game Boy, and Game Boy Pocket consoles.