DOODLE! Anybody singing "Do not...." within my earshot gets shot in the ear.
And yes, yella is of mixed race, from the time when negroes were valued higher the more "white master race" blood was in 'em. Not that sailors were racist, in fact, like cowboys, a hell of a lot of 'em WERE black. And some of the finest shanties owe a lot to the coloured influence (and most of THEM included un-politically correct language)