r5426 /src/mame/video/snes.c: [SNES]: Fixed direct color gfxs in mode 3/4, also fixed color data shifting in both modes.
Many thanks to Lord Nightmare for the save file.
Color shifting is the first thing that MESS does what other snes emus don't afaik. Ideally if you should do a color conversion to a framebuffer and you can't completely fill that framebuffer, you should fill the remaining data with the most significant bytes of the color offsets.
Comparison:
before: after: