I'm not sure this issue is quite as black and white as you suggest, ho-ho. I'm English so it's not really my affair, but under the last President, I'd have painted the place grey....more for his personality than his cerebral matter. Under Nixon, it was a nice shade of whitewash. Under Clinton, it was whatever colour Bill decided to tell you it was.
As a Limey, I confess to not knowing immediately WHAT colour I'd paint it during an Obama presidency. This has nothing to do with his ethnicity and everything to do with his vague 'direction'. Do you as Americans think you know what he's about? The Obamafication of politics is all very well, but 'Yes we can' gives me about as much clue as 'no we can't'. I thought our New Labour had topped anything for vacuity with 'Forward not back', but the mighty Barack trumped that one.
So I suppose the final, final answer from me is that under an Obama administration the White House would be painted all the colours of the spectrum. Or all the colours of a chamelion - whichever is the greater.
Trust me, either of these options would be better than painting Parliament Brown.
Good luck JW