There is a tutorial included in the template I think...
But it is pretty easy anyways:
(click to show/hide)
make a layer of pure black (#000000)
select that fill and lines, right click, "convert to symbol" -> choose a name or just say ok
in the properties window go into the "<Instance Name>" textbox and write rgbFill for the first color choice of the player or rgbFill2 for the second one(you could use that one for the pink stripes I guess, but as said before, you gotta make them black and let the user choose the color, or give it a default char-code containing this color)
if you want shading (like that grey-ish the pants seem to have, or the glare) put it in another layer on top of the black-tint layer -> with alpha, to let the color below shine through
I guess that's about it, hope I didn't forget anything