I've got a question about flashes. Must the color of the flashes coordinate with the colors of the kilt, or can the match with another article of clothing?

My kilt is a SWK Nightstalker so I ussaully wear black flashes, but I've worn my kilt with a white shirt, and a brown, herringbone vest. So, if I wear the vest, can I also wear brown flashes?

This is with black shoes, black sporran, and black belt of course. I was thinking I'd match this up with off-white hose.