You have a greater tool - your PC - that can be helpful to get the printouts of diverse colorful sheets. Guide the children, exclusively during the holidays to add illustrations to the colorful-page, and showcase them around the prominent places of the house. This will give them, a sense of pride and joy for their creativity, and would lead to further productive pursuits. Thus, you will witness that there are massive advantages of coloring-page relatively to coloring books. Coloring sheet are economical, costing you only a couple of cents in ink and paper rather than a few dollars for a coloring book.
Researches have shown that outdoor activities prove to be a good learning process for kids. You can take your child to a zoo to let him/her interpret nature with the help of coloring pages. Earth worksheets, pages for coloring, or activity books can be a good option for parents and preschool teachers. Pages with food drawings, animated drawings, alphabets drawings, and many more are also available online that can be used as a printouts.