Sporting grey skin instead of the familiar green, and not much bigger than a pro wrestler, the Hulk's first appearance also featured a decidedly different trigger for Bruce Banner's transformation. Instead of intense stress or rage, creators Stan Lee and Jack Kirby took another page from the horror movie playbook and used dusk and dawn to bring about the metamorphosis.
As it turned out, the Hulk's grey skin color was problematic for both colorist Stan Goldberg and the printer, so by issue #2 his trademark green skin was here to stay. It also didn't take long for the sun-based transformations to give way to the rage and stress-fueled hulk-outs.
In the years following the gray-to-green switch, reprints of issue #1 re-colored the Hulk's skin green...seemingly erasing the original gray model from comic book history. That is, until creator John Byrne reaffirmed in issue #318 (1986) that the Hulk was indeed gray at the very beginning, which lead to an extended run of issues by Peter David that featured a cunning Gray-skinned Goliath calling himself "Joe Fixit". Proof positive that even somewhat out-of-focus "humble beginnings" can be used to create clever new directions for familiar characters.