I remember like, years ago watching this video by Keinan Lafferty (I think) on youtube, and used the 'banana method' or whatever he called it in that, which is essentially making a curved 'banana' shape on your colour picker

essentially, the idea is, using your base colour (or, mid tone), you progressively shift the colour lighter and more de-saturated for your lighter tones, and inversely shift progressively darker and more de-saturated from your mid-tone for your shadows.

You can see in my colour-picked example here that it is not a perfect semi-circle, but it was generally the basis for how I'd pick colours, and then would tweak them from there.

How I'd tweak the colours usually is with the help of overlaying gradient maps. I'd also tweak colours in especially shadows, where I'd intentionally use a slightly lighter grey for the illusion of 'cooler' tones in shadows, and darker more saturated tones along the edges where the shadow meets the light.

I've more recently started trying out using triadic colour schemes, where I pretty much jump to the opposite side of the colour wheel for my shadows and light.

This image on twitter sort of sparked my inspiration to experiment more with that (image is linked to the original post) but I am still trying to get the hang of it still 🥲

When you're sitting behind a stall while selling your work at an art event, you just wanna do stuff with your hands in the downtime .... Here's a bunch of doodle pages from two events I was at recently lol. just half-thinking doodles. Yet I think they turned out kinda fun :D