I voted Yellow. This combination witht the black screen and yellow theme makes it look awesome.
I would like to see the grey in person too and compare the 920 to the 820. I think 4.5 is perhaps a little too much.
Ideally - cyan (they've teased about it at 38 second mark in this vid, who knows if it's real...), failing that, red looks nice but if the gloss is too scratchable or slippery then think I'll end up going for grey because I think it's meant to be matte finish?