Suppose that a node $x$ is inserted into a red-black tree with
RB-INSERTand then is immediately deleted with
RB-DELETE. Is the resulting red-black tree the same as the initial red-black tree? Justify your answer.
It's not, necessarily.
Informally, (1) there is more than one way to color the same tree and (2) nothing in the functions strives to accomplish a canonical coloring. In fact, all the functions try to do as little work as possible.
Here's a counter-example: