Real Color only give you real world airline liveries for the planes (and only if you already own the Real Traffic add-on). RC does NOT include the airport. I agree it is a little confusing if you are a new customer. Here is a priority list; each item on the list requires all of the items above it:
1. Tower3D or Tower 3D Pro (both products are stand alone and will work with all of the add-ons and include fictional aircraft ans airlines by default)
2. Add-on airports only require that you own #1
3. Real Traffic replaces the fictional aircraft models that come with the base game with a much larger variety of real aircraft models (but all aircraft are painted white).
4. Real Color packs add real world aircraft liveries to the aircraft that come with Real Traffic above, and WILL NOT work without it. Here is the trick, though. Each RC product (labeled by airport) will work with all airports in the game (both default and add-on). A given pack includes liveries for all airlines known to fly to/from a specific airport (many of these pack do overlap). Thus if you buy the pack for KATL, you will get liveries for nearly all Delta Airlines planes, as well as some Southwest, United, and a number of international airlines, all of which will work at KLAX, KSFO, KJFK etc.). This means that you do not need to buy every RC pack in order to have a large number of real liveries on most of your aircraft at most of your airports. Even if you own all of the airports add-ons, 3-5 RC packs will give you liveries for most of the aircraft in the game, depending on which packs you buy, although you will occasionally see a white aircraft periodically it is not in the sets you have.
Hope this helps.