How did the term blue plate special originate?

The food writer Daniel Rogov claims that the phrase "Blue-Plate Special" was first used on 22 October 1892, on a menu of a Fred Harvey restaurant on the Atchison, Topeka, and Santa Fe Railroad. It is an American colloquial expression. It became popular in the 1920's, a time when blue dishes were a common. It refers to a specially-low-priced meal, usually changing daily.