I've only seen the 8.5mm in red.
I had a spark plug boot blow out, on a fairly new set - I guess
the header heat degraded the insulation.
Since the other wires were ok, I bought a 25' roll or wire($32) and a few
end pieces($1.50ea) - It was cheaper to do this than buy another set.
Plus I can always make a spare wire if I have to.
I wised up and also picked up a roll of tube insulation to fend off the
heat at the headers.
