Character mistake: The archbishop wears a red zucco on his head at the dinner. Purple is the color of a bishop or archbishop. Red is the color of a cardinal.
Suggested correction: Generally true, but the specifics are not straightforward. The problem lies in the interpretation of "purple." Depending on the source, the purple may actually be "amaranth red" (which is a reddish-purple, but may look more like fuschia) or "magenta" (which may appear to be a reddish-purple or a purplish-red). Magenta is an equal mixture of red and blue, so the result should look somewhere between red and purple. How these colors or blends are perceived on screen may vary with the tint setting.
Also, it may be possible that the more reddish-looking zuccetto was meant to be and match the choir's red.
