Phantom of the Opera Costume Question (Pertains to the Novel)

I’ve not read the book in some time, but I recall that at the Masquerade, it was said that while the Phantom dressed as the Red Death, Christine and Raoul dressed as “dominoes.”

I’m assuming they were not dressed as little white rectangles with dots on the ends. If not this, though, then what?

My thanks to whomever can answer this.

A domino is a pretty generic kind of masquerade costume consisting of a hooded cape and a half-mask. Imagine a simplified Zorro costume and you won’t be far off.

The cloak.

http://www.probertencyclopaedia.com/PB.HTM

And there’s an illustration.

The mask.
http://www.broadwaycostumes.com/images/sales/m-9s-zoom.jpg
http://www.arneswarehouse.com/costumes/554-501.jpg

Misc.
http://www.umich.edu/~ece/student_projects/masquerade/commonalities.html