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Personally there are better ways to do this, change the color of the tech log/ipad for ETOPS aircraft. One black, one orange, mechanics and pilots know the drill at a glance.
I don't know how universal this is, but I've noticed that Delta has a rather prominent "ETOPS" painted large letters on the nose of the aircraft - forward of the nose gear. Readily observable during walkaround and by the ground crew prior to dispatch so long as they bother looking.