Feeling shy to tell your partner that you are in the mood for sex? Well, your lip colour might just do the trick for you.

A new lipstick has gone on sale that shows when women are in the mood for sex.

In fact, the gloss changes from clear to deep crimson as the wearer feels frisky.

Invented in California, the Mood Swing Emotionally Activated Lip Gloss works by reacting with a girl's body chemistry.

Priced at 12 pounds each, the tube comes with a colour chart so men can work out how randy their partner is feeling.

"The colours change depending on your emotional state," the Sun quoted a spokesman for makers Too Faced as saying.

Celeb fans of the gloss include singer Katy Perry, engaged to randy funnyman Russell Brand. (ANI)