a couple of tips for when you color in are.....
. if lock alpha is applied you can not go out of the lines. When you have a tablet it's easier but when using a mouse (which i used to have to used, and it isn't fun) it will help a little
. You can try some shading. Say a dog is standing on all fours. You can put a little shading on the inside of the legs not facing you.
I hope this helped a little. I know i am defanitly not the best artist and i'm learning on just about shading but these are just some biginner tips to help.
Enjoy
