Found a few scattered about the car now that I'm digging deeper.
Suspension springs I've mentioned elsewhere but they're also on other components - I know Peugeot used them on the 205 to make different specced parts that are visually identical easier to distinguish apart, presumably it's something others did too.
Some of the MK2 spring dabs can be deciphered using 7Zap but I've noticed if you're looking via a mobile the relevant column doesn't show, may need to view on a PC if you can't initially see anything useful.
Front Springs (https://volkswagen.7zap.com/en/rdw/golf/go/1991-110/4/411-102000/#1)
Rear Springs (https://volkswagen.7zap.com/en/rdw/golf/go/1991-110/5/511-106010/)
Rear spring of my 1991 8v -
(https://lirp.cdn-website.com/521a0932/dms3rep/multi/opt/shock+R-1920w.jpg)
These are on the drive shafts -
(https://lirp.cdn-website.com/521a0932/dms3rep/multi/opt/dshafts-1920w.jpg)
And engine sub-frame -
(https://lirp.cdn-website.com/521a0932/dms3rep/multi/opt/xmember-1920w.jpg)
Oh yeah, I'd noticed the paint marks, but never thought what they were for!
I'm wondering if it's a quality control pass of the individual item. The colour is possibly not important/has no meaning. It's the fact it's passed and been 'blobbed'. The items with multiple blobs maybe needed to pass different QC tests. ???
Or as you say, maybe the colour the is important factor. At first glance a spring from a 1.3 wouldn't look that different to a spring form a DERV or GTI although rated differently.
Would be great to know of someone that worked in the factory 30-40 years ago.
Follow up.... interestingly the paint dots were recently questioned on Club GTI which was then linked through to this thread.
Sorry to take you guys away from this forum...
https://www.clubgti.com/forums/index.php?threads/mk2-oem-spring-rates-here-more.218281/#post-1933734