I imagine Orianna has some kind of plain-colored tunic over her chain armor, heavy leather boots, and probably some leather pants under her chain. Most of it is probably drab colors, and since she bears her holy symbol on her shield she otherwise doesn't have any other outward signs of her status as a paladin on her clothes. She's not really focused on appearing nice or anything, mostly practical, though she does try to keep everything in decent repair. Everything on her is probably very clean, since she has prestidigitation she probably cleans all her belongings regularly. We haven't gotten any big changes to basic wardrobe or worn equipment yet so I imagine she's still probably wearing exactly the same things she was when this mission started, just maintained and repaired over time.