Things I Learned While Making Webcomics

Trees are green.

No, really. I mean, that seems obvious right? But when you draw trees, and you go to colour the trunk, what colour do you use?

It's brown isn't it? You're going to use brown aren't you?

Don't. Stop right there.

You see, if you use brown as your base, going lighter is going to take you into the yellows and oranges. Which is fine if your tree is all by itself on a hill in bright sunlight or something. But in a forest? Go with green, trust me. Your leaves are (most likely) going to be green, and since the complementary colour to green is red those orange highlights are going to get an impressive boost and be the most eye-catching things in the picture. So for a nice background use a yellow-greenish brown, and darker green-browns for the shadows, even go into blues a bit. for the lights use a lighter brown-brown-green, and you can finish with some (tiny) yellow-brown for the highlights (only where direct sunlight will hit it).

The second thing I learned from making webcomics is to colour your pages in order, that way you don't discover six random pages out of eleven in that you've been colouring trees wrong.
(I went 2, 3, 4, 7, 1 and that was where I found out how to colour trees.)

Always go in order, then you can excuse earlier goofs as learning from experience.