- Not sure if you're still looking for a color palette given that you already got a couple, but here's what I was able to draft up relatively quickly!
For the redline, I loosened up his pose a bit as he seemed to be very stiff in the original drawing! This effect is achieved by making the shoulders slope more downward and by letting the arms separate from the body somewhat. I also drew his hair much fluffier to give it more of a sense of mass rather than letting it lie perfectly flat to the head. These two tricks are very useful to make your art feel more "alive" and natural!
I really like his expression in the original drawing - it gave him a cool, but approachable, vibe. To capture this in his palette, I use darker, warmer tones as well as giving him that flashy highlight in his hair. I hope I interpreted his character correctly, and that you like the result!