Why do astronauts always use white suits?

Space is a dangerous environment and presents extremes of both hot and cold for the human explorer. To allow spacesuit cooling (and heating) systems to work most efficiently, they are made of material that reflects much of the incident radiation (mostly sunlight) that falls on them; hence, they are white. Another reason for using white material is that this helps astronauts to be visible to crew members, even in the darkness of the Earth’s shadow.