The first "super hero's" crest was designed in a shield shape to display protection and used primary colours due to the limited allowed pallet for comic book printing. As time went on, the shield became more abstracted with a focus on the famous "S" in the center. This increased recognizability of the logo while still keeping with the traditional style. In 1948 the logo first began to exhibit the modern shape and design and the colour choices were officially errated to tie into Superman's back story as the "Last son of Krypton." The yellow and red was said to be for the sun god of Krypton.
In June 1940 the superman logo became the five sided pentagon because it was easier to draw and read.