When you turn in your sketches on the 12th, you are definitely free to create separate color studies for your sketches (instead of putting the color directly onto your sketches). It's up to you! James Gurney is a big fan of color studies, here's a couple of his loose painted ones:
And, for some inspiration for your eyeballs, here's Dadu Shin's amazing tumblr of fashion sketches. It really shows how playing with volume in clothes can have a huge visual impact: http://idontlikeclothes.tumblr.com/
(c) Dadu Shin
See you on the 12th!!