Reader Carl sent in these photos from this year's Precious Blood procession in Bruges

In this first photo you see the bishop with two of his canons in proper dress: Black cassock, rochet and black silk mozzetta with red buttons and piping.

This photo raises two questions: Why is the black bishop not wearing a purple cassock (or is he no bishop)? And why does the canon to the left wear a purple cassock? Help!

And is this just some canon who does not belong to the Bruges Cathedral chapter or did he get it all wrong (purple cassock; no-silk mozzetta)? Help again!