Jeanette MacDonald is referred to as a blonde early on in the dialogue. She was actually a redhead, and no attempt was made to lighten her hair to make her look blonde. Her hair photographed the dark grey red hair usually reproduced as on the black-and-white film used in 1930.
When Rudolph is leaving the Countess's boudoir after kissing her and depositing her on the chaise-lounge, the shadow of the microphone boom can be seen on the door.