As already mentioned free coloring pages are a great way to teach your child all sorts of things, numbers for example. There are different ways this can be done, one way would be to simply have the number somewhere on the page, such as the number 10, and then somewhere else on the page would be an object or animal cleverly twisted into that number. There could also simply be 10 of something on the page, you can get your child to color the page in and then count out how many apples for example there are, which will obviously correspond to the number on the page.
Another advantage of coloring pages is that they provide your child with the chance to strengthen their hand eye coordination, as they learn to color in the lines. This skill will develop gradually as they go from struggling to stay inside the lines, to perfecting this fine motor activity.