How does Juliet appear in the party at night?

When Romeo first sees Juliet at the Capulet party, he is captivated by her beauty. He says she stands out like a bright, jeweled earring against a background that, in comparison to her shining appearance, is like the black ear of an Ethiopian. He also compares her to a snowy white dove walking with a group of black crows. He says that he has never loved anyone before (apparently forgetting about Rosaline) and that he never saw a truly beautiful woman prior to this night. The passage in which he speaks of her is as follows:

Oh, she doth teach the torches to burn bright!
It seems she hangs upon the cheek of night
Like a rich jewel in an Ethiope’s ear,
Beauty too rich for use, for earth too dear.
So shows a snowy dove trooping with crows
As yonder lady o'er her fellows shows.

Interestingly, Romeo doesn't offer specific details about Juliet beyond saying that her beauty is dazzling. We don't, for example, know the color of her hair or eyes or what she is wearing. We do know, however, that her physical beauty is what motivates him to fall in love.