Thank you! Colors are mostly intuitive, so I’m not sure I have much to offer in the way of instruction. I’m trying to learn more about it, myself, so I can make art more intentionally. A few things I’m trying to pay more attention to:
How warm & cool tones interact, where they are on the color wheel relative to each other, value scale, and how saturated and chromatic, ex: warm light, cool neutral middle tones, cool shadow setup (you can switch these up to different effect). It’s a bit rigid and simplistic, and doesn’t always hold up to realistic light conditions but it’s an easy way to start containing colors within stylized illustration; you can fine-tune it as you learn more.
Neutral tones! They support and draw attention to more chromatic colors, giving places for the viewer’s eye to rest. Lots of colors can qualify as neutral depending on your chosen palette. For example, if you’re working digitally, use the eyedropper on some colors that read as “grey” and you might find they’re actually green, if the main colors are pink/red.
Regarding value, think of “molding” shapes dimensionally and imagining how they interact with your designated light source. Drawing fundamentals are integral to a well-structured painting (think of it like the skeleton), but painting is a different approach than contour drawing. No one wants to hear this but… painting from life really is the #1 way to train your eye. Set up still lifes of stuff you actually want to paint under different light conditions to make the exercise less boring! (I like to paint desserts hahaha.)
When I’m in photoshop, I always fill the topmost layer with black and set it to “color,” turning it on periodically so I can check my values. Lifesaver.
Lastly, everyone recommends Color & Light by James Gurney, and it’s hands-down the best resource I’ve come across! Inexpensive and concisely covers a broad range of topics like this with visual examples that the artist painted himself. (And it’s got a funky dino on the cover, what’s not to love??) His blog’s interesting, too.