Wiktionary
blend in
vb. 1 (context transitive English) To add (an ingredient) by mixing or blending. 2 (context intransitive often followed by "with" English) To fit unnoticed into a surrounding.
WordNet
Usage examples of "blend in".
Just learn the game, learn how to blend in, and be sober while seeming less than sober, and they would only notice that he had beaten them after it was accomplished and he was gone.
He toyed with the ceremonial dagger he wore at his side, reduced in size to blend in with his civilian station but offering traditional comfort just the same.
Maybe Trinli was simply an aging criminal doing his best to blend in and survive.