An oligarch like Berzins in Latvia can - hopefully! - not be seen as a real GREEN, thus VanDerBellen were the first. More difficult: SalzburgCity, the home-town of me (and roughly also of our "Tender Branson") claims, that it had the first GREEN executive worldwide (1982). "Joschka" Fischer in Hessia was sworn in 1983, but does anyone know an earlier GREEN minister?
In the Netherlands, the Politieke Partij Radicalen (Political Party of Radicals) participated in the Den Uyl government (1973-1977). The PPR later merged into GroenLinks in 1989, and was during its existence a party with a 'green' agenda.
In the early 80s some of the more 'Fundi' greenies left the PPR to form De Groenen, but that party has never been successful (although it still exists).