I head canon that, when they retire to South Downs, that Crowley just goes nuts with colors because he’s not tied to Hell much anymore and their dress code was always bland and sad. He goes on a shopping spree, mostly online, and every day there’s a new set of clothes being delivered to their cottage.
Actual colorful paisley designs, lots of bright plaid (which he calls Tartan just to annoy Aziraphale haha), Hawaiian shirts, some with pineapples, martini glasses, pink flamingos, surf boards, like all out gaudy fucking colors. For the winter, he gets big parkas with faux fur that are bright orange. Aziraphale (who takes up knitting) makes him brightly colored beanie caps and scarves.
Aziraphale loves every bit of his new style and certainly indulges him, even though he himself isn’t too particular for loud colors.