I always pictured them being the sort of yellowy-tan color they are on the cover, which is weird. I think maybe she described them as looking like centipedes (though I googled and a lot of centipedes are not that color) maybe that is where I got it from.
Anyway as for being killed be can openers, yeah, I always got the impression you could kill a Taxxon with just about anything. A can opener, a baseball bat, a plastic spork. (Ok maybe not the spork but pretty close.) I believe they were described like a wet paper bag but I might be mis-remembering. It's time for a reread.