Get it? It's a pun on red Solo cups. And his name is Solo. Also, it's a solo project. Either way, it's the best advertisement for the iconic plastic cup company since Toby Keith's 2011 single "Red Solo Cup" or the invention of beer pong.
It's important to note that Red Cup obviously won't be the actual title of the film, it's just the place-filler title that production uses until Disney announces the real name closer to the time of release.
Almost every entry in the Star Wars franchise has had an interesting working title. Return of the Jedi was famously called "Blue Harvest," The Phantom Menace was "The Doll House," Attack of the Clones was called "Cue Ball," Revenge of the Sith was known as "The Bridge," and The Force Awakens had the working title "Avco" -- named after the theater director J.J. Abrams watched his first Star Wars movie as a kid.
"I'm really excited to work with him. I think he's going to be great in the role," Ehrenreich shared. "I think he's awesome. He's such an interesting guy and a wonderful actor, and I think he's just going to do something with that role that is going to be really exciting for everybody."