@inkandspatter You've probably heard this before, but getting the values right is really the first key. I'm still not great at this when I am working in color, so I find that it really helps me to separate light layers and local color layers and tweak them. I have been treating it almost like I'm lighting for a movie, or in a 3D program rather than "painting" in a sense.
I like to also keep a layer on top of everything that I can turn on or off to see things in black and white. I often think one value is quite a bit darker than another (say I'm doing a reddish shadow and a bluish light side) but when I turn on the b/w layer, it becomes obvious that this isn't true! Once I fix that, the piece always looks way better.
Another thing that I've finally learned recently as I've been studying light more, is that being mindful of how the secondary colors (yellow, cyan, magenta) are all brighter colors (at their most saturated) than the primary colors (red, green, blue). So if I want to have a really saturated light side, I need to stay with the secondary colors, whereas if I want a really saturated shadow, it works best to stick to the primary colors. Other than that, I just have a process where I can continue to tweak the colors endlessly until I'm like it. I usually change the color scheme several times while I'm painting.
I'm still (always I guess) learning about light and color myself, but I've been drawing and painting in black and white for a long time. Actually, recently I've been going back to black and white to just reinforce the value structure again for myself. I feel like you can't do too many value studies.
Hope some of that can be of help to you!
