Hi! Sorry for answering so late. Holidays and a lot of work after...
we bought the tiles with the concrete optic in a shop in the near of munich, the shop is called REMO in stilhof. They have their own spezialiced names for the tiles. But you can ask them or write them an email.
http://www.stilhof.de.
hope, I could help you a bit. best regards, susi
Q
Bad gray color
Q