No matter what the theme or the picture, all a child - or the young at heart - needs is the page and something to color with. Pencils, crayons, markers, watercolor paints, chalk. There are coloring books made specially to be used with water-colors, that come with their own little set of paints and brush, and have thicker pages.
The material. Some coloring books offer the ability for the child to simply run over the surface with the pens or crayons provided, and it will turn out to be the right color regardless. Some are more like paint books, and some have magic marker surfaces and come with markers that will not show up on any surface but the specially prepared book pages. Choose the book that best suits you and your child. If you are worried about markings on the walls, then don't select a pack of basic crayons, get something that uses special crayons. If you want your child to exercise their own creativity and not have to fit in the lines or color schemes planned, get basic pages. It is up to you.
Nowadays the World Wide Web made simple getting information. And color by number books reap benefits of the web progress.
Believe it or not, there is now a way for children to create their very own iron-on transfers with some new technology that has been developed. The Magic Color Page is transfer paper that has been specially developed for kids. They can draw on this transfer paper just as if they were creating their own picture in a coloring book.
Best of all of course are free pages that can be printed out at home any time you like. There is so much variety obtainable that as long as they have their pages and something to color with a child will never get bored. For many children, there is no greater gift they can give to Mom or Dad than a picture they coloured all by themselves. Inside or outside of the lines, any page coloured with love and happiness is a masterpiece.
Occasionally, you'll find official cartoon or TV character sites (such as PBS programs) will make available coloring pages for free to their fans. And there are many other sites that distribute coloring pages of those copyrighted characters. Sounds like dangerous legal ground ...but, surprisingly, I've never heard of any of these sites being prosecuted for copyright infringement. So they'll probably continue to make them available.
Today the World Wide Web simplified getting necessary info. And coloring printables took advantage of the web progress.