Our Sturt has red/brown and green panels on the walls, and a darkish creme (still a fairly light shade) on the roof.
I reckon that's a good combo, as the dark walls don't show dirt/marks very much, and the lighter coloured roof is a bit cooler in the direct sun.
All of the canvas is pretty heavy so light transmission isn't really a factor.
That said, in the summer, the heat coming through the roof gets me out of bed before the brightness worries me.