Template:Venn diagrams of parity relations

In Venn diagrams like these black areas tell that there are no elements
and red areas (marked with a cross) tell that there is at least one element

Parity relations don't tell if there is nothing or something, but just if there is an even or odd number of elements:

This Venn diagram		tells that there is an even number of elements in the intersection,
while this one		tells that the number of elements is odd.