The caption reads "The only reason to vote black." Yeah, that's what I said.

After we got the reader tip on this one, you know I had to investigate. According to Spiegel Online International:

The poster put up by the environmental Greens party in the western town of Kaarst contains a play on words: "Black" in German party politics refers to the color colloquially used to describe Chancellor Angela Merkel's conservative Christian Democratic Union (CDU) party. Other major parties are described as red, yellow and, of course, green.

The poster is meant to highlight the Greens' support for same-sex partnerships, said the local head of the Greens, Christian Gaumitz, according to the daily Rheinische Post.

German Green Party Defends 'Racist' Campaign Poster [Spiegel]