/ic/ - Artwork/Critique

Requesting critique for my thumbnailing process. In normal paintings i go straight to color (starting with super unsaturated colors like Mike Azevedo does), but with these iterations i decided to follow the advice of pros and do the values thumbs first and then just apply color schemes to them with the Color blending mode.
The result, however, looks extremely shitty - unpredictable colors all over the place, i have now idea on how to control them except for going in manually and redoing every single thumbnail.
So the question is, what should i fix/practice to have color thumbs that can be shown to art director/client as a final choice before the rendering? Should i also have a cleaner lineart for them?
Also if anyone have good examples or artists that do and post these online, please share them.