Surely a few decals or a one off paint job wouldn't have been too much....its a really important milestone.
Every Loganair Saab I saw at EDI yesterday was sporting a rather large "50 Years serving Scotland" decal on the side of the fuselage. Today at EDI they had/have balloons decorating every flybe check in desk and the ticket desk as well as free stickers and pens for passengers (who wish to take them, of course) and a few mugs going as well. There's also some stickers for car windows being given out. So there has been some effort for the celebrations.