Welcome to the forum !
RGB stands for Red Green and Blue (RGB) and its a option US gives us, so you can select your blade colours (7 combos) on the spot. 3 Extra buttons, so its like: Look! I'm a jedi ! (klick) Look! now im a Sith !
I sugest you go to
www.ultrasabers.com and look at some of the videos they have under the "Ultra Saber video" section, and look for RGB, or search this forum more

We all had questions, some of them are darn specific, and you can find all answers allready on the forum, otherwise just ask, and we can help, If not, Ulstra is allknowing

PS: good time for a RGB option too, since US has a sale ! Only 60 bucsk extra, and you basicly get 7 "sabers" !!