Counterexample on blue ribbons signifying marriage from the Pace-Egging song of the Watersons: Oh the first to come in was Lord Nelson you see
With a bunch of blue ribbons tied round by his knee
ANd a star on his breast that like silver does shine
And he hopes you'll remember it's pace-egging time

Lord Nelson's marital doings, as C.S. Forester remarks, were "the laughingstock of the fleet"; he abandoned his wife of about 15 years to live in a menage a trois with Emma Hamilton and her elderly husband till Sir William died; Nelson never went back to his wife and lived with Lady H. whenever he was on shore (which wasn't much) till he was killed 194 years ago last Thursday. Anyway-- even though there's that verse in The trees they do go high about tying blue ribbons, don't think it necessarily had that meaning.