I sometimes use Pixlr for some stuff.
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Tip #1 - I would at least smudge some stuff (but don't get it outside the lines.)
Tip #2 - I kind of like to combine colors a lot. It helps.
Tip #3 - I use the brush to design but I outline the lines with a pencil XD
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Q: How do you get colour?
A: Color like the color to use the tools (that has optional colors on them?) You click at the bottom of the tool sidebar. There should be a box and smaller boxes beneath with smaller boxes with color. Click on a box and choose your color!