Sonder is German for special. Thus, these are special models, offered at the beginning of Summer 1984.
All Sonders shown here were produced in very limited number for the '84/'85 model year, except for Helios, which continued through 1986.
Almond Beige and Firnblau are extremely rare, if Volkswagen even ever put these two colors into production. While Havanna Brown Metallic paint is not rare, this particular sondermodell is.
The Havanna and Helios Blue Sondermodells are not to be confused with the 1985 Havanna and Azur models; the latter two come with completely different interiors from the Sonders.
Volkswagen gave the Helios Blue Sondermodell the nickname "Mr. Moon" in January 1986 and sold it in the UK as well (as a GTI).
While the Sonder brochure shows and lists white and black special models, these are listed on their own respective pages: White Edition, Black Edition.