It is years since I saw one of those... the red and green are one, and the flats on it were for a large spanner to fit in order to tighten the assembly into the threads on the housing, the washer with tabs on it some of them bent, is designed to stop the large blue nut from unscrewing.. If you look at the housing it screws into you may see a raised rib to the rear acting as an anchor point to bend a tab on either side of it..
The ribbed rubber acts as a spring to stop accidental engagement of reverse and is held slightly compressed by a C clip on the top of it fitting into a ring cut into the shaft . It was not uncommon for those to have damaged threads ending up with the gearstick coming adrift. I think there were different colour nuts which denoted different thread types (?) perhaps imperial or metric... And that is about as much as I can remember, I am NO expert.
