

I’m not aware of any heat-trapping properties of the colour white, other than it’ll reflect visible light.
It reflects emr in the visible spectrum. It probably reflects emr slightly beyond the visible spectrum too, like infrared. Then you make a tube out of it and put a hot body in the tube. It will reflect the war back at the body.



It depends on whether you’re standing in direct sunlight for extended periods of time or not. Generally, staying in direct sunlight for extended periods of time is going to do so much to you that the albedo of your shirt isn’t going to really do too much.