I can't find a picture on Flickr to prove it, but I'm sure that the new X18 Enviro's have different coloured seats to the rest of the MAX vehicles, I think the headrests might be blue?
I know this is a bit picky, but customers will notice if they get off one bus and go onto another that is duller etc.
RE: Arriva North East: Latest News & Discussion - March 2015