The computer and the internet have opened an entirely new spectrum of coloring and drawing. Adults now make very sizable livings creating, drawing and coloring pictures for computer animation including video games, movies, commercials and items most adults would never consider, such as some high-quality information websites. With this option available as a full-fledged career for adults, it is no wonder that the tools and formats used in this style of artwork have carried down to children, albeit on a smaller scale.
You can metaphorically take a page out of a coloring book, and break up the work into a few sections. Each team member or group within the team should first be instructed on which part of the page they are going to color, let them know what color they can use, and when their turn will come up. Next, after each team member has finished their part of the coloring than take the completed picture and hangs it up so that every one can see their part of the picture and the entire teams contribution.