just remembered this very useful thread that would be worth a read.
http://www.iceinspace.com.au/forum/s...ad.php?t=83503
re the colour of materials, almost all paints (and most other materials except metal) are pretty black at thermal IR wavelengths, so colour is not important for radiation efficiency - it does make a difference to absorption of sunlight though. The differences in apparent temperatures of a variety of materials under cold sky is likely to be due to thermal conductivity rather than colour - they transfer heat to the surface at different rates.