In an interview with Netflix Korea, Hwang and the show’s costume designer, Chae Kyung-Sun, explained the meaning behind the contest employees’ red jumpsuits, and specifically the symbols on their masks. It seems that just like society overall has a hierarchy, the game’s organizers have a class system, too. Overall, Hwang and Chae wanted the workers to seem like ants in an ant colony, which is how they landed on the jumpsuits. “At first, I wanted a boy scout-like outfit but it showed the men’s figures too well,” Hwang explained. “It didn’t really make them look like ants in an ant colony. They needed to cover their entire body. And the best option to keep them anonymous was a jumpsuit. With a hoodie too, because they need to cover their faces (via KoreaBoo).” And just like ants in a colony, the employees have designated roles, which are denoted by the marks on their masks. “Circles are workers, triangles represent armed soldiers, while squares are for managers,” Hwang explained (per Somag News).
As for why those specific symbols were chosen, it’s because they represent letters of the Korean alphabet. The circle is the letter “O,” the triangle is part of the letter “J,” and the square is the letter “M.” And “OJM” are the initials for the Korean name for the squid game, “Ojingeo Geim” (via The Tab).
That’s one mystery solved, but many more are still unexplained. Hopefully we’ll get more answers if and when we get “Squid Game” Season 2.