Are you struggling with the colors in your illustrations? I really was a time ago. For a long time I was using colors just appealing to my taste, producing works with different grades of quality, but with no real guides to follow. Fear not! There are guides and simple rules to keep you in the good path to produce mesmerizing pieces of art. Here are my favorite tutorials I found on the internet to introduce you in the amazing world of colors. All of them are oriented to digital painting, but you can use the theory for the traditional media too.
1.- Color theory for designers — a crash course (with infographic)