Concerning 'The Leaboy's Lassie' mentioned by Marje above:

I suppose this indicates that at that time, bright colours were a sign of lax morals in a woman.

Two sources mention red and yellow as the colours of the 'Lichtbobs', who were a regiment of the Light Brigade (David Buchan, Folksongs 151) / the Somerset Light Infantry (Fraser, Edward / Gibbons, John (comp.): Soldier and sailor words and phrases 190). There is no indication of the meaning given by Marje, but maybe it went without saying at the time that a woman following a soldier must be 'fast'?