A Game Boy (Color) emulator for Windows, based on GEST v1.1.1 by TM, with added support for unlicensed mappers, Unicode filenames, screenshots and some other stuff.
When playing an SGB-enabled game that changes the border, then loading another SGB-enabled game that does not immediately change the border, the border from the first game persists.
Solution: loading a game should clear the SGB border.
Reported by NewRisingSun