Hi Louis
Just to let you know that although I don't exactly know why we have moles, the hairs that grow out of them means they are healthy as my Husband has a large amount and the doctor has informed him that they are not malignent if hair is seen coming out (but don't panic if you have a mole without a hair, it doesn't suggest it's cancerous!)
I would imagine (but I'm not sure) that moles are excess pigment in the skin and as the hair grows through the darker skin it is also darker. I suppose there is almost always hair growing out of moles because there is hair all over the body, even if it's really light.