That's not the only big costume callback — Jon Snow's new outfit in episode four was actually blue and brown Stark armor.
In episode three, we saw Jon easing back into his Stark roots with an outfit similar to his season-one getup — but it was still all black. But in "The Book of the Stranger," we saw Jon finally embrace the full Stark colors. The blue undershirt with a brown padded gambeson is the same uniform Ned and Robb Stark wore in earlier seasons.