In an "imaginary story" (non-cannon stories, usually taking place in another realities), in Superman # 162, Superman decided to increase his intelligence, so he could finish his list of unaccomplished goals, such as returning Kandor to it's normal size. He did so via a machine powered by kryptonite. It made the Man of Steel 100 times smarter, but it also spilt him into two Superman-beings: Superman Red and Superman Blue. They successfully restored Kandor, but they didn't stop there. They re-created Krypton (dubbed "New Krypton") and in the process destroyed all existing kryptonite. The duo made an "anti-evil ray", designed to remove criminal tendencies from people. They used satellites to emit the ray causing not only Mr. Mxyzptlk and Lex Luthor become to good, but even Communists. The now-good Lex created a serum able to cure all known illnesses and placed in the water supply. Now that Earth became a paradise, Superman-Blue married Lana Lang, Superman-Red married Lois and even Jimmy Olsen married Lucy Lane at the same wedding. Superman-Red decided to go live on new Krypton (giving up his powers), while Superman-Blue stayed on Earth and started "Super-Family". This version of Red and Blue were seen in Infinite Crisis # 5, when Lex tried to fuse all the alternate reality Supermen together and in Superman / Batman # 25 in an army of different versions of Batman and Superman.
"Superman Red/Superman Blue"
The next version of the duo began in a 1998 storyline, where Superman got electric-based powers, later it forced him to wear a blue containment suit. He could turn the powers "off", but became as vulnerable as a normal human. Some fans call this version "Electric Blue Superman". In the Superman Red/Superman Blue one-shot, the Cyborg Superman created a trap that split Superman into a rash Superman Red and a cerebral Superman Blue. The two started to differ from each other so much, that they didn't want to turn back into the "normal" Superman. Both Supermen fought over Lois Lane, so she kicked them out her house. Perplexed, both Red and Blue went to Antarctica to see if the Kryptonian tech could help solve the issue. But, they found a woman called Obsession, previously known to have romantic lust for Superman at an insane level. Then, Maxima (another super-powered Superman-admirer) came to the scene. Although Obsession liked the idea of two Supermen, Maxima was completely opposed to it. The two woman fought over this. The Supermen stopped the fight by separating them. After battling the Millennium Giants, the two Supermen fused together. Why this happened is very vague: Superman felt "rewarded" for saving the Earth, but he later claimed to haved turned back when his "electromagnetic energy dispersed". However when he was battling Brainiac 13, in a later comic, Brainiac 2.5 manage to turn him into the "Electric Blue Superman" to stop 13.