On a trip to South Carolina last spring, I fell in love with the blue porch ceilings all over the place. I am not sure why they are painted blue, but our tour guide told us it's so birds won't build a nest on the porch. (Apparently if birds look up and see blue they will think it is the sky?)
I don't believe him.
Here is what my google search found for the perfect porch blue:
Benjamin Moore's Arctic Blue
Martha Stewart C26 Porch Ceiling Blue (pictured above)
Sherwin-Williams SW 6471 Hazel, SW 6505 Atmospheric, or SW 6944 Pool Blue