Generally, the first few episodes of any new show devote a certain amount of time to developing the stars' "look." By mid season, it's not uncommon to actually find it changed completely. I remember someone saying once that Whedon wasn't really sure just what he wanted to do with Angel at first, so the velvet coat might've been an idea that just didn't work out. Buffy started off with those mini skirts and boots, great for showing off shapely legs, but a high kick filmed from the wrong angle, and the Moral Majority is calling for the show's cancellation. White nail polish and purple ring, I didn't notice (did I mention those short skirts), but I do seem to recall Angel looking like he was wearing eye shadow, which sort of goes with the aforementioned velvet coat...