No orange vests for railway work. The standard issue (for us) is green. We have to change to orange for railways in case we get mistaken for a green signal.
True story, I was once refused access to a London Underground switch room for wearing a green vest. I was told that the train driver might mistake me for a green light etc. The switch room was at street level next to the booking office. I said that if the train driver got that close to me, last thing he would be thinking about is lights, red green or any other colour. I was still thrown out though.