Yes that filter is accessible through obj_game->"censor" in the table I shared previously. It starts at 0 and goes up to 0.95 as the background gets darkened. I can mod that, but I don't understand the ask, do you want it to stay at 0 ? or at 1 ? (above the game's normal maximum)
at 0:
View attachment 3286742
at 0.95: (game's default)
View attachment 3286745
at 1:
View attachment 3286748
As for the image with inverted colors, yes that's also controlled by the game code, it simply applies an inverted filter to the current sprite. I roughly know how to control it.