You are thinking too much on your shading by adding too many colors, instead of trying to use it for perspective.
Your color choice is also very soft values which makes your shading look soft. In your attempt to make it less gradient, you just removed shading, rather than actually fixing it.
Your shading is very cell shaded, there is no obvious light source. which makes the image look rather unrealistic.
This is my version of a janitor, I would recommend starting off smaller. Your sprite is rather giant. why make it harder on yourself?
Look at my colors of choice, mainly on the jumpsuit. Think selectively about your colors, ask yourself, do I really need this color in the piece, or do I really want the color? If you answer yes to these questions then probably keep them, otherwise you'd probably be safe, and better off not including them.