In most women, the genital areas will be darker than other skin. There is no "normal" colored vagina, vulva or anus. Simply, the skin in that area is darker.
This change in tissue color is caused by a higher amount of melanocytes – the cells that secrete melanin (pigment that provides color). Melanocytes naturally increase in the genital areas with age and/or states of increases in or vacillating estrogen levels. (A perfect example is pregnancy.) In addition, excessive friction or rubbing of tissues can also result in an increase of melanocytes and darkening of the genital areas. This may occur with obesity and the rubbing of skin or increased activity. Consequently, it is completely normal for genitals to darken with age.
As reported by Dr. Sabine Wunschmann is perfectly normal genitals darken with age.
Adding that "is a blessing to grow up and even better to grow up beautiful "