It is easy to show that in-order traversal is not sufficient, by providing a counter-example:
5B
3R 10B
1B 4B
3B
1B 5R
4B 10B
These are both valid red-black trees whose in-order traversal order is (1,3,4,5,10). Thus, it is impossible to reconstruct a red-black tree by only an in-order traversal of its nodes.