But for a Printing Error, the Incredible Hulk Would Be Grey
I guess every Hulk fan can be thankful that process control in printing in 1962 wasn't what it is today.
Stan Lee, the creator of the Incredible Hulk, originally envisioned a grey-skinned hulk. Lee chose grey for the Hulk because he didn't want to reference any particular ethnic group. The problem: The run of the premier issue, in which the images of hulk printed inconsistently in a wide variety of grey and green tones as one read through the issue. The green ones struck a chord, even though they were a mistake.
It is easy to imagine how this printing error occurred. If one wanted grey and instead got green, the density on press was either light on magenta or heavy on some combination of cyan and yellow. After seeing the first published issue with the sometimes-greenish skin, Lee changed the Hulk's skin tone to green, and amended the storyline to reflect that change for future incarnations of the comic book.
Since the Hulk's green skin exists as fundamental to the character's zeitgeist, it is was a serendipitous error indeed: The latest 2008 Hulk movie alone made a whopping $263 million worldwide at the box office, with estimates of the total revenue steam generated from the character in excess of a billion dollars since its inception.
Some folks, and printers, have all the luck.