I recommend that you install a disconnecting means at the new outlet - either a combo receptacle/breaker housing or a separate breaker or switch (suitably rated) in a weatherproof box/enclosure adjacent to the new recept.
If you are doing this 100% to code, you probably need to do a load calculation which would include the existing home's load plus the new RV outlet. It could be possible that by calc. you can't do a 50 amp outlet. But do you really need the full 50 amps at home? You *could* wire it all up for 50 amps (incl. wire) and install a 2p-30 amp breaker in the house panel - which you could always upgrade to 2p-50 amps later on.
A red wire would be nice and just personal preference and won't help except for maybe doing a diagnostic check some day. It's not like you have a switch leg or 3-phase. But you can simply take some red electricians tape and wrap it near the ends of the black wire.