I also thought it was probably for Pentecost, but that it still looked gaudy and just a little too "70's hip" for a Prince of the Church to be wearing.
I suggest you take a look at the vestments worn during the 17th and 18th centuries. Quite "gaudy" all of them. It was the baroque style. And I will take "Anglican." beats the "hip' garments I saw in the '70s.