In the ISS, they don't wear blue clothes only :
There seems to be a preferation of khaki pants, but there is one in light blue too.
Sorry, I found no information about the deep blue jump suits worn on Earth.
Another orbit image added by Organic Module:
(not even in the shuttle)
I have only casually spoken with a few (maybe six) former astronauts while I was visiting the Kennedy Space Center at Cape Canaveral. From my conversations with those former travelers into “space” (beyond earth’s gravity), with me inquiring about any self proclaimed atheists of those who have escaped earth’s gravity into outer space, the former astronauts ...