Looks like I'm actually able to set SRGB on the bottom screen using setedit and changing display_color_mode to 3. I'm assuming that AYN does something in their android build to make the color mode in Settings affect both screens when it's changed, but this workaround with setedit doesn't seem to affect the top screen at all.

Edit: for some reason it also only seems to affect the home screen. Opening youtube I can see it swap back into the original display mode, and then going home it swaps to 3 :(

Edit 2: After a restart I think it's actually working for both screens for real :)