I don't know much about the flashing yellow and red. I haven't seen them in Vancouver before. I try to avoid Po/Co as much as possible. :) But your friend, if he/she drives, would know.

Oh wait, flashing arrows? A flashing arrow means you can turn. If it's yellow it means "caution" and stop if you can. If it's red it means you can't turn (even if the non-arrow light is green).