you guys are totally gonna laugh but i have a tub labeled "paper scraps" and i have the kiddos trained.
if they only use a portion of the paper, fine. but then they must cut the extra off and add it to the scrap tub. even little 1 inch pieces get saved. (foam felt and tissue paper too) then, when they know they only need a small piece for something, say, two black eyes, they have to take it out of the scrap tub.
free art doesnt mean free to waste
LOL
but seriously, i think half the fun is digging around the scrap tub for "just the right piece". they love it...
as far as coloring books, i would make them finish the picture, or limit the number of pages you give out.