Why do some people have darker moles than others?

Hereditary: Generally, one with darker skin type (has ability to make a lot of pigment), will tend to produce moles that make more pigment. One who has very light complexion will less likely develop very dark moles. Regardless, i always encourage routine self exams as instructed in the following link: http://www.Aad.Org/skin-conditions/skin-cancer-detection/about-skin-self-exams/how-to-examine-your-skin.

More pigment: Pigment is the chemical in the skin that determines color. Some people have more than others. There are also different types of moles. If a mole changes colors, has more than one color, has irregular borders, or gets bigger than a pencil eraser, it should be examined by a doctor.