In this situation piste colour is largely irrelevant. It appears that the slide came from a steep slope above the piste. Due to piste machines and skier activity the snow is heavily compacted and unlikely to avalanche on-piste. If there are steep slopes above a piste which receive a critical amount of new snow through wind deposit or precipitation there is a danger they can slide onto a piste (regardless of what colour the piste happens to be).
It happens a few times a season. Two years ago a child was killed in an avalanche (that he or his parents set off) which ended up crossing a piste in
Davos, Switzerland. I seem to remember at least one (possible two) slides crossing pistes in
Zermatt in recent years and also in other resorts in the Valais in Switzerland. I saw some small slides reaching the edge of the piste in Lenzerheide, Switzerland two weeks ago.
The resorts tend to do their best to bomb potential avalanche dangers close to pistes but sometimes the bombing might bring nothing down and a skier passing through might still release something. (I've seen this happen in the past too!)
It would be interesting to know if that slide was spontaneous or skier triggered.