Red Black Tree Properties:

1. A valid binary search tree.
2. Every Node is either Red or Black.
3. The number of black nodes is the same along every path from a fixed node to every descendent null reference.
4. Red nodes can't have a red node as a child.
5. The root node is always set to black.

Example and more information:

Here is an example of a valid Red Black Tree:

Here is more information about Red Black Trees: Link here.