A lot of the colours here are very similar, so even though you're using many colours, you're getting very little value out of them - both literally (they span a small value range) and figuratively (each colour contributes very little to the piece). I saw this sprite in your WIP thread and thought the character was overwhelmed by the scenery because their colours are so dull.

There are two remedies, best used in unison: Push the values more (darker darks, possibly lighter light colours if that's appropriate), and hue-shift your shadows and highlights (add another hue to your shadows, adding more of it for the even-darker values, and possibly another to the highlights, again getting stronger the further away you get from your midtone/base colours). Both of these will make your colours more interesting and create more contrast, which will make the sprite easier to read.

Hue-shifting, if done consistently, also has the added benefit of making your colours more unified with each other since they're become tied to the same colour or two, which can make it easier to work with colours on nearly-opposite ends of the colour wheel like you've done here. You're being quite daring with the colour choices here and that's awesome, but you'll need a little more work to make them all click together.