generel observation and paying good attention to the imagary that i like has sorta got me where i am now. (also I went to a art/animation school for 3,5 years)
I use gradient and texture overlays for my digital art. trying different things out. drawing and observing all (- most of) the time will help.
I also use color tools like this
[link] for inspiration - and here is a color test tool
[link]