When Thor is detained, Loki briefly appears wearing a jacket, dress shirt, tie, scarf and long overcoat:
(Click to enlarge)
This is outwardly similar to his Stuttgart disguise in The Avengers, though the scarf is quite different (as are the shirt and tie, to a lesser degree).
It’s difficult for me to tell if this costume has a green-ish tint to it, of if that’s just a result of lighting. If it is, here’s my attempt to correct the color balance: