Derek

The unnamed man in pink is a resident of Gravity Falls and a former member of the Blind Eye Society.

Season 1
In "Boss Mabel," he could be seen in the background of the Cash Wheel Set, together with the "Unnamed woman in blue".

Season 2
In "Scary-oke," he can be seen at th the grand reopening of the Mystery Shack.

He can be seen playing golf at the "Ye Royal Discount Putt Hut", in "The Golf War".

In "Society of the Blind Eye," it is revealed that he is a member of the Blind Eye Society. He is seen walking out of the museum after Dipper erased the memories of the society members.

Appearance
The unnamed man in pink has short reddish-brown hair, wears a pink shirt, brown pants and has prominent chin.