blue laws refers to set of laws layed down in one of the NE colonies-- that were for some reason-- written on blue paper-- many of the laws concerned alcohol consuption and sale, and what could or could not be done on the sabbath..

the blue paper was a special process to paper making-- and the same blue paper was used to wrap up "Sugar loaves"-- (shaped like sugar loaf mountain (Brazil?)) it was an expensive paper.

(I like to think it was NY that had the laws first written on the blue paper, and it was my fair city that gave rise to the term-- but i have no facts to back me up!)