I was in the Palais Garnier last summer for the POB's La fille mal gardee. Many men wear no coats. It is not really that dressy. I may have worn a coat but it was during the 105 degree heatwave and Paris has no AC. Unless it is a gala, I see no reason to wear more than a coat and tie.
The Chagall ceiling
I picked up a cream colored silk formal shirt from Budd. The cloth is thick and densely woven and lacks the cold silky smoothness of the typical silk shirt. I think it wears well for the winter, but too hot for other climes.
The cream color is not particularly noticeable at night.