I'm trying to work on environments and digital painting/colouring in particular. I honestly have no idea what I'm doing, so any pointers on workflow, technique, or to any tutorials would be greatly appreciated. I used Jellyfish-Station's lineart, as I was rather lazy and wanted to start right away. Keep in mind this is INCREDIBLY rough, I'm just figuring out the light source and how it affects everything at this point.
Instead of going straight into coloring something from mind, how about you do some studies from life and read about some basic color theory first? And even before that your priority should be to get the values (shadow placement!) right: Light does not shine around corners. If you have a light source you must stick with it, which in this case means that the entire character, save for a bright outline, the top of the right leg/foot and hat will be in shadow. You might wanna try is cel-shading with multiply and overlay layers to get a feel for it :)
Real general pointer for coloring: do values first, with big brushes, because that'll help you figure out lightsource and everything much more easily.
Try it! Basically, work in greyscale, using a big brush, minding the contrast and using it to make your focal point stand out.