Red marks the spot.

Berlin bans red triangle symbol used by Hamas to mark targets – Berlin has banned the inverted red triangle symbol due to its use by Hamas and their supporters to mark enemy targets in videos and graffiti.
The motion passed in the state senate said the scarlet arrow icon represents an immediate threat to Jews and to people committed to the freedom and security of Israel and should be banned at protests and in the context of the Middle East conflict.
The symbol has been used to target pro-Israel academics and politicians, including Kai Wegner, the Berlin mayor who ordered the eviction of pro-Palestine protesters from the city’s Free University by police.
“Kai will pay” was graffitied on the wall of a university under a red triangle.