Gearboy is an open source emulator for the Game Boy Color written in C++. Gearyboy has a highly accurate CPU emulation, including accurate instruction timing.
To prove its accuracy the Gearboy team have tested it against blaargs “cpu_instrs.gb” test and “instr_timing.gb” test. The emulator even goes as far to also emulate the LCD controller, so everything is drawn to the screen as it would of been on the Game Boy Color.
Gearboy maintains support for all common memory bank controllers and their associated RAM cartridges.
While this emulator is highly compatible with original Game Boy games, to a point its Game Boy Color side is not as accurately produced and not as compatible or emulated.