The current psychedelic CPM is pretty hard on the eyes. Even having a single constant colour for objects, clearly distinct from the grey of terrain, would be an improvement on this.
But how about going one step further? We could give all the major types of object their own colour -- e.g. red for fire, blue for water, purple for traps, green for exit (maybe green for both hatch and exit since they are usually easy to distinguish from each other) and yellow for miscellaneous stuff like splitters, teleporters....