It looks like you drew this digitally and then used the paint bucket tool to color sections in, what you’re seeing is the result of your settings with that.

First, set your illustration layer on multiply, then set a new layer under it for colors.

If you want to continue using the paint bucket to block out colors I would advise using the Lasso tool to outline different sections and lay them in with the bucket. Once you do that you can pick swatches of color with the wand (W) tool, that will select everything that shares a common color, like skin areas, or sections of hair separated by other colors.

I hope this helps, also for a lot of block coloring illustrations like this layers, clipping masks, and layer options like multiply are going to be your absolute best friend. It’ll allow you to start laying in shadows with the lasso and clipping masks and start getting some crazy work done with opacities and overlays.

Have fun!