I actually haven't heard of lioden before 😭

I mainly try to use colors that go well with the character by looking at color wheels and look at what colors match, if you ever wanna do any outside (or space, beach, ocean ect) bgs id reccomed getting some pictures that have the same vibe you want for the bg + practicing always improves everything Also when i make designs i useally get a basic idea of what tones of colors i want to use,(warm tones, cold tones, neutral tones etc) putting overlays over the coloring can make all the colors join together :] i can totally explain how to do it if you want

That took a while to wright lol

Sorry for late responce but a overlay is basically putting a single color on low opactity and covering the entire coloring over it :] You just have to copy and paste the coloring on a new layer, then you lower the opactity on the color by the bar under the color bar then you press the icon that looks like a mechanical pencil, it makes it so you only color in what has been drawn on that layer :]