Today most homes have a printer on hand and that makes it fast and easy to use online printable coloring pages. They don't take much ink either so you can find the value is there all the way around. If you don't have a printer at home you can often use those at the local library to print the coloring pages for a very small fee.
With online printable coloring pages you never have to keep volumes of coloring books around. Most children change what they would like to color often. They bounce around from one theme or one set of characters to the next. Therefore they may abandon that coloring book with princesses or cars days after you buy it. Printing out the pages though allows them to always get what they want.