Objective: Describe the way color is utilized in each artwork, specially color contrasts.  Then contrast these uses in both paintings.
I suggest you visit http://en.wikipedia.org/wiki/Color_theory to learn some art terms about color.  It is kinda dry and drawn out, but you basically need the following: primary, secondary, tertiary; cool vs. warm; tints and shades; shadows and pigments.

You might also want to check out http://en.wikipedia.org/wiki/List_of_colors just because it amused me and it might amuse you.