How did the blue laws get there name?

"Blue nose" or "Blue noses" was an insulting term applied to people who wanted to regulate the lives of all society to their own standards (today we would say "control freak"). In this case, christians who enacted laws that attempted to force Sunday as a day of rest on the population as a whole - sort of the "Keep holy the lord's day" kind of thing. Since blue noses supposed these laws, they became blue laws.
Scholars today reject the idea that blue laws were so named because they were printed on blue paper as untrue.