Hello again,
I use HWE (ninja, diamondback and extracta) and dry fusion cleaning systems.
My understanding is that the colour fade was not immediately apparent (purple colour tile, dark when wet, dried patchy and streaky) and that a carpet cleaner had staff doing the work for him, not supervising himself at the time.
I was told the story and shown the tile at a Dry Fusion training day, the point being made was that the Dry Fusion Chemical did not remove the colour from the tile, and so was safe to clean them with.
I also would not have expected a carpet tile to lose colour, and I rarely check them for colour fastness,although I do now
Chris