Clew, you are having another "episode" of brilliance. 100% spot on observations and great detail with the images.
I believe the organism (fungi or ...?) feeds off bacteria, and thrives either as a predator or in symbiosis with worms as well as borellia. It isn't very contagious because most bodies aren't a suitable enough environment for an infestation that is bad enough to manifest obvious symptoms.
That red fiber is going to wrap up those towel fibers, then cinch and goo them into a single thick strand that is coated in goo - just like it does to our hair. What color is the towel?
Yeah, stronger M infections involve more colorful matter, but I haven't yet made any correlation with certain colors being more "dominant". I still think the organism just sucks whatever threads are on the skin in to use for protection/habitat or... I recently put raw bacon on a hotspot behind my ear for 10 minutes, and three blue fibers entered the bacon. Not surprisingly, they were colored the same as my hoody from that day.