nostr:nprofile1qy2hwumn8ghj7un9d3shjtnyd968gmewwp6kyqpqpfj27ps0mky9d9vn5c87qvz586fehdw26wxx477dr3v36yhauleqgfpfyz Bits 3 and 4 of the PPUMASK register. https://www.nesdev.org/wiki/PPU_registers#PPUMASK_-_Rendering_settings_($2001_write)
I made a function to do it…