[1] https://petapixel.com/2023/04/12/pentax-unveils-k-3-iii-mono...
Or I think one could argue that Foveon X3 sensors are monochromatic... "More like YCbCr" or something.
1: https://hackaday.com/2021/08/09/using-a-laser-to-blast-away-...