Our boat has green trim, so our full canvas is dark green. On cold winter days the full canvas, closed up tight, is a solar heater in the bright sun. We often heat the boat by leaving everything buttoned up, turn our stern to the sun, leave the cabin door open, and warm up the 'house.'
We have had thirty degree mornings for the past few weeks -- oooh, so nice to have the Wallas purring and then the sun shining and warming the canvas enclosed cockpit (our Grandkids, when they were aboard with us in Yellowstone, called the cockpit their "back bedroom" and loved the warmth of early morning.