You could use the magic wand tool to select areas and change colors (I would put a layer behind inserting the new color or colors there).
The magic wand is located on the tools, to toggle tools on or off pull down the file window at the top.
You can adjust the grabbing or opacity or power level of the wand, at the top look for a sliding scale, also holding the ctrl key while using the magic wand allows you to select multiple areas.
and on the anything else that's cool question..
There are endless cool things like ...ummm lets see...
Shape3D is cool you take a picture and render it 3D and looks cool.
Julia Fractal is cool...
Overall it will take some trial and error... once you get it you have it.
A term you will need to know
"install plugin"