John Leguizamo initially turned down the role for Benny Blanco four times as he didn’t want to get typecast as another Latin drug dealer. The role nearly went to Benicio del Toro. He eventually agreed to do the part under one condition; he was given freedom to improvise and make script changes that would alter Benny’s backstory.
In the novel the film is based on, Benny was less layered and more of a simple, hot headed drug dealer. Leguizamo changed him in one fundamental way - he made him a Carlito Brigante superfan. Benny idolized Carlito from a very young. He grew up hearing stories about how he ran Spanish Harlem and how he was connected to the mob. He was so infatuated with him he's literally starstruck when he first sees him (see below).
This is why Carlito’s dismissal of him was so devastating to Benny. He had built his whole identity around Carlito, only to be humiliated and brushed off. That humiliation leads to rage, which becomes the driving force of Benny’s character, and what ultimately leads to Carlito’s demise.
Benny represents the greatest threat to Carlito: time catching up with him. He is, in many ways, Carlito as a younger man - without the honor or criminal codes that defined him. And this is why he’s so dangerous, and it’s why he’s dressed in red when we are first introduced to him, because in the world of Carlito’s Way, red signals danger…(1/5)