When women in the use of sex toys, because the labia for a long time by external friction and serious stimulation, will secret a large number of hormones, to a large extent caused local pigmentation gradually calm, in its color will be with the passage of time and slowly become deep, this is a normal female physiological phenomenon.
The color of the female vagina is mainly determined by its own melanin precipitation, which has a great relationship with female hormones. The degree of color is mainly different from person to person, with their own amount of pigment also has a very large relationship. Some people who do not have a lot of pigmentation will keep the color of their private parts, even if they use sex toys many times.
If we get more pigmentation simply because we use sex toys more often, surely we don't rub our hands less than we do when we have sex?