Yes, standard DE-CIX route server BGP control communities apply to blackholes as well. You can e.g. signal a blackhole to all route server peers except AS64501 by setting the following communities:
(6695:6695) where 6695 is the AS of the DE-CIX route servers in Frankfurt.
Replace this to the corresponding route server AS of each DE-CIX IX.
For more information about route server BGP control communities, please have a look at our route server guides.