I've got it on the roof but wish I'd added some to the walls.
However the wall lining I added since provides a heap of insulation.
Sounds like a nice colour scheme Spooky. I had the same idea. Red walls to match the red brick of our house, cream trim and doors to match. We used the same colour and profile colorbond for the roof as the house too.
I've got a bunch of clear poly carbonate sheets on the roof. They have a tinted version which looks a similar color to the gray colourbond we used. I've got them over the top and a couple on the sides above my machine shop area. Lighting is great during the day but doesn't seem to get too hot. I think one of the advantages of the barn style is all the heat rises up into the top of the center area. Down on the sides stays relatively cool
Cheers