Legally no, post 65 buses should display amber indicators to the rear but it does seem to depend on the MOT testers interpretation of the rules and the phrase 'as originally fitted' etc etc.
Personally I swapped them over to Amber lamps in the reverse lights on Hank and they are so much safer when on the motorway, very glad of them last night on the haul back from Brighton to the midlands in the dark :mrgreen: