Mandala is known worldwide symbol of universe and it is mostly known in Indian regions. I think that mandala coloring pages are more for adults than they are for kids. Please see below for some of the best mandala coloring pages.
The symbol actually stands for "Peace" in a very loose way. It was designed by artist Gerald Holton and incorporates the 2 hand-held semiphore symbols for "N" and "D" which stands for "Nuclear Disarmament".