I am led to believe that the 'Blood red roses' refered to here are the redcoats being carried overseas on boats. The sailors, being dressed in whites or blues, refered to the soldiers, possibly marines, by this term because of the colour of their uniform coats.

Don't realy know if it is true but makes some sort of sense if you accept that the song is a shanty or at least of nautical origins.

Cheers

Dave the Gnome