Rainbow Legacy Challenge

I hope you don't mind if I reply on an old thread but there's something I never understood about the Rainbow legacy: are you supposed to start with a single Sim that has Red hair/clothing? And do you kill the first generation when you're "finished" with them?

I keep seeing households on the Gallery that have Sims (up tp 8) that are already dressed as Rainbow but I didn't understand if you're supposed to play them all at the same time...?