The Game Boy Color made Pokémon Crystal the first Pokémon game incompatible with the original Game Boy. Pokémon Crystal was released in Japan in December 2000 and internationally during 2001.
Unlike Pokémon Gold and Silver, Crystal was designed specifically for the Game Boy Color’s improved hardware. Its enhanced color capabilities supported animated Pokémon sprites during battles, additional visual presentation, and other technical improvements.
Crystal also added important gameplay features. Players could choose a female protagonist, visit a Battle Tower, and follow a story that gave Suicune a larger role. It was an enhanced edition of Gold and Silver rather than a completely new generation.
The incompatibility is easy to confuse with ordinary color support. Pokémon Gold and Silver could run on both the original Game Boy and Game Boy Color, although they displayed in limited color on the older system. Crystal required the newer Game Boy Color hardware, making it a technical milestone in the series.