A dum dum tries to explain her coloring process.
I do my coloring digitally on Clip Studio Paint. My technique can be implemented on other programs like Photoshop, SAI, Medibang, etc since it is not so complicated, just a matter to have the hand and attention to detail
1. Once the lineart is done I do the flat/base color
2. With a dark, not so saturated purple I do the soft shadows with airbrush, then lower opacity to my desired % in a multiply layer
3. With a dark, not so saturated magenta I do the solid shadows, with a diluted watercolor brush again in another multiply layer
4. Then with a tone lighter than the base, I use the airbrush again in a luminosity layer to do highlights and balance with the shadows.
5. Finally, details with a darker pencil brush, again with a tone lighter than the base in a luminosity layer to do a few details.