I think Oda has given the distinction if you see Rayleigh's introduction.
Right hand and First mate(Vice captain) aren't the same ,hence he made Rayleigh be both The First mate and the Right hand.
There would be no reason to mention both.
Red-orange Vice-captain.
Green Right hand.
The world saw him as the right hand and that's why I think Oda put it inside quotation marks,while the Vice captain was his internal role in the crew.
Marco also has only the Right hand unless I missed it.
The colour spread is about the The Second strongest-the Right hands.