The original Superman-Red/Superman-Blue tale is an “Imaginary Story” that first appeared in Superman #162 (July 1963). The script was written by Leo Dorfman, with art by Curt Swan.
In the story, Superman is compelled to finish a list of unaccomplished goals, including the enlargement of the Bottle City of Kandor and eliminating crime and evil from Earth. In order to accomplish these goals, Superman invents a machine, powered by various types of kryptonite, that will increase his intelligence. The machine works, increasing Superman’s intelligence a hundredfold, but with the unexpected side effect of splitting Superman into twin beings, one outfitted in an all-red Superman costume and the other in an all-blue version. The twins name themselves Superman-Red and Superman-Blue.