I really dislike this whole screen is red thing. I read your statement about level theme but you could do something else such as only make the platforms, walls and blocks red but keep the background and character in normal color.
Viewing post in How does this pixel art image look?
Player characters, movable platforms, enemies, items, items you can interact with, should catch the eye somehow (either via contrast, color or HUD markers), these are basic UX/UI guidelines. Maybe play around with contrast and saturation, playing with different red hues? E.g. make the player neon red while the background has a slightly less saturated red?