There are pigments in the skin that react to light. As an Afro-American, (a dark skinned), I can be in the sunlight for an hour with not problems where as my very fair skin sister would get spots, or freckles, and the lightest skinned people would turn brown or ever receive burns. The important thing is to protect you skin of any color. Skin cancer is a big threat. Even my people should protect their skin. If brown spots are smooth, they are considered freckles. If it is raised in any way it is considered a mole. Moles need to be watched for color change and shape. If this happens, the person should see their Doctor very soon. Moles can turn ruff, and grow wild and not be cancerous, but chances are it is and you will need a Doctor to consult.