What color backdrop is good for a studio portrait?

I’m doing my first real studio shoot of a model. I’m not sure what she will wear, but usually she likes bright clothes. I just asked for no white clothes because it might through off my meter readings (since the lights are going to be set up in advance.)
My professor had one rule, which is no white backdrops. So the question is neutral gray or black?
The lighting is going to be three quarters Rembrandt lighting with a reflector fill.
Any other suggestions besides the initial one about the backdrop are welcome.

Currently I use black or chroma-key green … with white you can use controlled lighting to make it various shades of gray.

Paper is good for times you want to cover wide areas (107″)

4 yards of yardage from you local Wal-mart from the $1 a yard table is good … or wide muslin at about $7 a yard and then you dye it.

Muslin usually has the most options if you want to buy “off the rack”

Look at these links for more backgrounds.

http://setshop.com/index.php?cPath=4_219&osCsid=1aa8bcc010da6c0f74028fdc5e4faff8

http://www.owens-originals.com/Standard%20Muslins.html

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