Bizarrely I've search under yellow and dots and found nowt! I'm not going to start again with blue bolts.
It does hoot about Self-locking, Nylon patched and Tribular (special threaded) but is careful to avoid any colour bias.
When I was in the fastener trade (many years ago!) painted (Organic) finished fasteners were specified because zinc based finishes were ecologically deemed bad. Cadmium was banned years ago except for aircraft fastener use.
Car manufacturers specified the colour for all sorts of reasons, usually simply for identification in critical areas, otherwise black or silver. Trilobular fasteners came in during the late 60s and were a huge advantage as they tapped their own perfect thread ( being shaped like a tap) & did not require a separate tapping operation ( even into blind holes in castings or rimmed punched holes). If unavailable for repair work a standard thread fastener of the right strength worked perfectly in the tapped hole.
Here endeth the lesson!
D
