Long before there was ever a title called “Elseworlds”, DC Comics stories that took place outside of the established timeline were known as an “Imaginary Tale” or an “Imaginary Novel”. This is a copy of Superman number 162 from 1963 in which Superman attempts to duplicate himself to solve the world’s problems. Subjecting himself to various forms of Kryptonite, he ends up splitting into two beings: Superman Red and Superman Blue.
This was the original Superman Red and Superman Blue story that influenced the 1990s incarnation.
The story was written by Leo Dorfman, penciled by Curt Swan, and inked by George Klein.