The sandy colour gets my vote.
Teh sand one looks too cheerful to me, for some reason I tend to like my sci-fi a little darker (not too grim dark but a little dark still)the blue is a good compromise I think as it's quite neutral and looks a bit more futuristic (in a retro kind of way) than the sand.The green one is the one I'd go with for a real darl ambiance with mixes of the three shades to break the monotony between buildings while retaining some coherenceIf you want a simpler answer, it'd be a tie between blue and dark green.
Thanks for your thoughts gents. I had begun leaning towards green, but over on LAF I noticed Matakishi has a very similar project and he's done his all grey. It looks better than I expected it would. So I'm thinking about that too now.
I reckon all three. I like the idea of all three colours together on each panel.
They're well under way in green at the moment. Pictures when I get enough done to show off!