Why does Lupin change jacket colors?

There is no in-story explanation, and that is the point worth documenting: the jacket color is a production signature. Each television era re-dressed Lupin to announce its tone, and the fandom learned to read the colors like vintages. Monkey Punch’s manga Lupin wears red, chosen, the artist said, because red is flashy and sexy. The anime then invented the sequence everyone now recites.

Critics at CBR and elsewhere have mapped the colors to temperament: green for the serious, empathetic thief; red for the broad, lecherous showman; pink for pure cartoon anarchy; blue for the modern, mellowed adventurer. The mapping holds because the productions really were that different from each other. The color is not trivia; it is the fastest accurate summary of which Lupin you are about to watch.