These days color by number books can be found in various forms. You could choose among different fairy tales characters and/or animals, autos and so on and so forth. If your child is in love with Winnie-the-Pooh, then you may find a lot of colour by number games with the heroes of this toon.
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.
Most homes will have coloring pencils or crayons. In my house we also have glitter pens, foam pens and most importantly paints for the kids to select between. Using paints will require a little bit more setup time as you may need to clear an area and lay newspapers down over the table to protect it.