When something is bloodless, it's free of violence. During a bloodless revolution, a regime is overthrown without anyone being killed.
A coup or a revolution is sometimes described as bloodless — in these instances, political and revolutionary goals are achieved without any blood being shed or lives being lost. A different meaning of bloodless is "drained of blood" or "pale and white," as your face might look if you saw a ghost. The Old English word was blodleas — figuratively, it meant "powerless."