unfortunately I don’t believe color palettes can change on an original gbc. The rom recognizes it’s on a color device and switches to the black and white color palette
Thank you so much for your prompt reply! Actually, with original GB games (like Pokémon Red/Blue), just press a directional button + A/B during the Game Boy Color logo startup screen, and you can have many different color palette variations.
I'd love for a future update to include an optional green color palette directly in the ROM, for those who play on GBC.