I already own a pair of these  great slide sandals in black patent.  That first pair are wonderfully comfortable, with excellent support for the foot,  slip-on, slip-off ease, and  a non-clunky ;The icy pearly onyx is, to my eyes , a slightly blued sort of grey, with a low metallic patina.  Nothing that shouts, so I thinks they'll be a nice neutral.  Good with jeans, fine with black or olive or....  These do make the slightest bit of noise, flip-fop style, if that would bother any of you who must walk in absolute silence.  On sizing, I'll offer this: in an ordinary sandal I wear an 8.5 medium.  In these, though, a 38 narrow gives me a perfect fit.  My foot is probably a little on the narrow side of medium, though, and i suspect not everyone with a medium width foot would want or need to order the narrow in this Birkenstock.  I look forward t wearing these often.  It's not sandal weather here yet, but they are in use already around the house.