No question bedevils a man more than whether his female companion is in the mood for a frolic. Now a new lipstick promises to tip off the state of a woman’s libido by changing color as she warms to his advances.

According the Sun, the Too Faced Mood Swing Emotionally Activated Lip Gloss starts clear. When it reaches deep crimson, the wearer is supposedly ready to rock and roll. The product isn’t cheap, however. On Amazon, where it is currently out of stock, it sells for $37 a tube.