Superman's costume was inspired by the Flying Graysons' circus troupe. Superman Smashes the Klan reveals that this Golden Age version of the hero's costume has roots in a surprising place. The Man of Steel and his family found some very interesting places to take notes on fashion from.
The costume that Superman wears is incredibly iconic, though it has had a few variations over the years. Superman Smashes the Klan draws from the hero's Golden Age iteration, placing the story in 1946. This three-issue limited series from 2019 focuses on Superman and a group of young people fighting the Clan of the Fiery Cross, who has been harassing an American Chinese family who moved from Metropolis' Chinatown to Metropolis proper. The series was selected as DC Book Club's read for the month of May 2021.
Superman Smashes the Klan is written by Gene Luen Yang with art by Gurihiru - the collective name of artistic duo Chifuyu Sasaki and Naoko Kawano. In this story, Clark Kent's story parallels that of Lan-Shin (Roberta) and Tommy Lee, the children of the Lee family that is being harassed. Flashbacks to Clark's childhood reveal that he felt very alienated in some ways due to his abilities. In one memory, a circus has come to Smallville and Clark goes with his parents and Lana Lang. While there, the future Man of Steel is inspired by the strongman in the circus. It just so happens though, that this is the same circus troupe that the Flying Graysons are a part of.
One panel in Superman Smashes the Klan #3 shows three acrobats in the same color scheme as Robin, with symbols matching those seen on the Flying Graysons in Batman The Animated Series and Young Justice (2011-2013) #6, which is based on the animated series. This circus troupe features the Mighty Samson, a strongman that Clark recognizes as the ticket taker, though Lana doesn't recognize him due to a wig and change in his demeanor. A fire starts at the circus, which causes Clark to leap into action to help Samson - this is Superman's origin story, not Robin's. While talking to Samson after the incident, Clark is inspired, and his mother handles the rest.
Samson tells Clark that he's got a future performing, but young Superman is afraid that others will fear him if they see what he can do. This is when Samson reveals the secret that changes Clark's life: wear a costume and make it bright. Generally, this might seem counterintuitive since wanting to blend in is not accomplished by wearing an attention-catching outfit. However, having a go-to outfit that protects the identity of the wearer and seems opposite of who they are is a great way to hide, without hiding at all. Ma Kent has the same idea and sews up a version for Clark, incorporating the Kryptonian symbol that was on her son's spaceship, and Superman is born. This moment is very interesting because it reveals that this costume was not purely Clark's idea initially in this iteration. It also provides a lot of context into his character and hesitance to assume a role as a superhero. The Flying Graysons' troupe influenced multiple heroes' lives - including Superman's.