"Presbyterian True Blue"
Context: Samuel Butler satirizes the Puritans in the person of Sir Hudibras, heightening the burlesque by explaining what a tremendously subtle philosopher he is: he is as learned as Alexander Hales, Thomas Aquinas, and Duns Scotus combined, being especially well versed in Nominalism and Realism–matters of great concern to the Puritans. He knows where Paradise is, what Adam dreamed about, whether Adam and Eve had navels, whether the serpent at the fall had cloven feet or none at all. As for his religion, he is a true blue Presbyterian. The term "true blue" is subject to several interpretations. In the light of the old adage, "True blue will never stain," it can mean that Hudibras was a stanch and faithful member of his sect. The term may also refer to the actual color blue, to the wearing of which the Presbyterians were greatly addicted; the preachers frequently wore blue aprons. The general sense of the passage is that Hudibras was an excellent Presbyterian. "True blue" now has the meaning of faithful or true. The passage in which the expression occurs is:
For his religion, it was fitTo match his learning and his wit;'Twas Presbyterian true blue;For he was of that stubborn crewOf errant saints, whom all men grantTo be the true Church Militant. . . .