I really enjoyed the atmosphere of the game and both characters control very well. The different abilities are a nice touch. As others have pointed out, the game is a little confusing at first. Putting the controls on the game's itch page or in the main menu would've helped me a lot because I was really confused by that lever at first. Also, on the red character I spent a little too many tries falling to my death because it wasn't always too clear where I could and couldn't go and so I jumped around a lot looking for a new path. Maybe make those death gaps a little more clear.
But overall, great job. If you want to develop this further with different level designs and more complex switch puzzles, it has the potential to become a very fun puzzle platformer.