Probably the easiest way to get a hold of pages for your kids to color is to print them out from websites online. There are plenty of sites that offer free downloadable coloring pages. Just search for "Christian coloring pages" or "Biblical coloring pages" in your favorite search engine, and you will find a bunch of results.
Websites arenot the only place you can get coloring pages. You can also find Biblical coloring pages and activity books at your local Christian bookstore or at some arts and crafts stores. Giving your child a coloring book of Bible stories is great, because it allows them to see the sequence of events.