Originally introduced in Action Comics 23 as a crazed Eurpean dictator, Luthor originally was portrayed with red hair.

Art by Joe Shuster and Paul Cassidy

But by October 1940, when Luthor first appeared in the daily comic strip, he was portrayed as bald. Art by Wayne Boring
By 1952, Ed Hamilton and Wayne Boring had turned Luthor into an overweight, business suited con-man.
Here he's selling Metropolis citizens protection from disasters he's created himself.

In April 1960, Jerry Siegel recast Luthor as Lex, a former childhood pal of Superboy's who vowed revenge after an unfortunate lab accident.

Adventure Comics 271
Art by Al Plastino

In Action comics 271, December 1960, Luthor began wearing a prison uniform pretty consistently, even when not in jail. 

"Voyage to Dimension X" by Otto Binder and Al Plastino.

Although Luthor was routinely portrayed as fat and out of shape in the 1950's, by 1963 he had slimmed down and built himself up to the point where a physical duel with a (non-Super) Superman was a possibility Superman feared.  Superman 164, Oct 1963 by Ed Hamilton, Curt Swan and George Klein.
In 1974, Luthor adopted his own colorful action uniform and tried to go toe to toe with the Man of Steel, using super science to duplicate Superman's powers.  From Superman 282, by Elliot Maggin, Curt Swan and Kurt Schaffenberger.