To expand those intellectual capabilities and help the brain grow coloring pages are a very good form of intellectual exercise.
The lowly printable coloring page is really a chance to show kids a lot of things about the world and best of all you can find coloring pages on just about every theme and idea and they are often free to print out. Printable coloring pages even work well in a pinch. If you have a bunch of kids over and only one unused coloring book left, it's easy enough to go online and print out as many copies of coloring pages as you need.
Oh and then when we got to our destination, the coloring pages were given as a gift to their Nan - so you can see how great this simple hobby is!