May well be others, but I'm thinking of the gearbox end cap, the gearbox inspection hole plug and these collars for the drive take off, whatever their proper name is, pictured below...
(https://lirp.cdn-website.com/521a0932/dms3rep/multi/opt/1-42029657-1920w.jpg)
All a similar green, got me thinking is it a way of high lighting single use items?
The end cap definitely is and the inspection plug may be as it's such a tight fit if screwed in completely that it's destroyed while getting it out.
Those collars, are they single use if taken off... might confirm what I'm thinking?
Interesting thought and perfectly feasible