If the entire universe is in one pixel, there is no single photon outside, so it is of course black!
But moreover from a quantum mechanics point of view, if there is nobody is outside the entire universe, there is no one observing something from the universe, so maybe the universe doesn't exist...(see this as an inspirement: <a href="http://www.iafe.uba.ar/e2e/phys230/history/moon.pdf" rel="nofollow">http://www.iafe.uba.ar/e2e/phys230/history/moon.pdf</a>)