If you do not have a sense of humour when it comes to the liturgy, do not follow this link. Blogger Catholicus offers a new development in the story of the Venerable Paul VI's morning Mass on the 18th May 1970.
Did it happen? I don't know. But if Catholicus is right, the red vestments were laid out, not for the Octave of Pentecost, but for the feast of Pope St John I, Martyr.