If you have only enough for half, might it look a bit strange to put
one color in the middle and the other around the edges?

How about simply alternating? I've seen alternating black and white,
for example, in catalogues, so it's got to look okay in person. Though
I don't know about how it might look if it's, say, patterned blue and
patterned red.

You can always simply lay them out without adhering them to the floor,
just to see what it might look like.

Shaun Eli
http://www.BrainChampagne.com
Brain Champagne: Clever Comedy for the Smart Mind (sm)