Since its introduction into Star Wars, the X-Wing has been a fan-favorite ship throughout the franchise. From Star Wars: A New Hope to Star Wars: The Rise of Skywalker, the fighter has been key to saving the galaxy. And most recognizable is Luke Skywalker's X-Wing, designated as "Red Five." However, when A New Hope first began filming, Luke's ship and call sign were different colors.
Red Squadron took part in the Battle of Yavin and the Battle of Endor, marking it as one of the most important groups in the Rebellion. Yet, within George Lucas' original screenplay, it was said to be Blue Squadron and Luke Skywalker to be Blue Five. His original X-Wing Model bore blue markings, and this version almost made it into the final film until problems started arising.
Because CGI wasn't an option when creating A New Hope, the team had to use a variety of groundbreaking effects and filming techniques to achieve the look. One way was to film the model ships against a blue screen, mask the blue and composite it with other pieces of film reel. Once all the separate layers of effects got placed together, it created the final product of multiple ships flying through space. And while this technique worked great for the time, it meant that the color blue had to get removed from all ships, or it would risk getting keyed out along with the blue screen.
So, the original Blue Squadron had to become Red Squadron. However, remnants of the original design still made it to the public. As George Lucas wrote the screenplay for A New Hope, the novelization got written by Alan Dean Foster and released several months before the movie. Within the novel, Luke is a part of Blue Squadron, and the Y-Wing Gold Squadron is said to be red.
While Blue Squadron got removed from the Original Trilogy, it's since returned within other Star Wars media. Within Rogue One: A Star Wars Story, Blue Squadron led an attack over the planet Scarif and was in charge of breaking the planetary shield and providing ground support. However, by the battle's end, most of the squad was gone, explaining its absence from the Battle of Yavin. And much later, in Star Wars: The Force Awakens, Poe Dameron took command of Blue Squadron during the attack on Starkiller Base.
Red Five has become an iconic call sign for Star Wars fans, but if it weren't for the filming techniques of the time, it would've been all blue throughout the franchise. Funnily enough, though, with the stories in current canon, Blue Squadron has far outlasted Red. In fact, the classic squadron has been out of action since the Battle of Endor, leaving many looking to past for stories of their favorite X-Wing squad.