Stuee,
My 101 is standard olive drab as is the canvas. In summer on the road with sides up it can still get to 45-50 inside the cab and is normally 15 degrees hotter than outside temp - you can feel the heat coming in through the canvas above the cab.
I would definitely not get a black canvas - the body colour you are looking at is close to a standard series 3 Landrover colour (Baby Puke Yellow) and in my view a Sand Colour or even Olive Drab canvas will match the body quite well - don't paint it as the canvas will breakdown after a time. Have a look at the All Wheel Trim site as they do great work.
All Wheel Trim Ltd. Land Rover 101FC page
Garry

