Sometimes used by Paramedics to describe someone who isn't oxygenating their blood properly and are literally, visably, the color blue (especially in the face.) Not sure why the color blue is, in this case, associated with boots. None the less, still something that is said.
"That guy was as blue as your boots, with an altered LOC (level of consciousness) and decreased vitals"
by Fudge911 December 10, 2009