Full on bold lips
Most Helpful Guy
I have read studies on human mating behaviour, which found that a woman's choice in lipstick changed according to the phase of her menstrual cycle.
By perhaps what is more than mere coincidence, the buttocks of the female howler monkey turn bright red when she is ovulating and ready to mate.
The same sort of thing happens in the human female.
When a woman paints her lips bright red, it is intended to reflect the colour of an aroused vulva and tell males that she is oestrous and ready to mate.
Those who had academic access to journals should be able to find plenty of material on this subject.0