A small child's intellectual capabilities begin to develop as soon it is born and by age 4 they have developed most of the basic capabilities they would require for their adulthood. The brain never stops growing though and keeps on assimilating and organizing the knowledge it had acquired.
In my household using Hello Kitty coloring pages is one of my kids most cherished activities. I think this is great as it is so low cost and easy to keep them entertained. Few activities for kids are as stress-free, that's for certain. In the modern busy world, this hobby is a calm oasis. Personally I enjoy the quiet moments that coloring brings. It is a welcome break from all the music and shouting that is so common with youngsters. Hello Kitty coloring pages especially continue to be one of the most popular and demanded by little ones of all ages, especially with young girls!
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.