Male, 17. Recently, the head of my penis change from a pink/red color to black. Not the whole head, just the tip of the penis, the area around the part where urine come out. It's not very noticeable unless seen in bright light. It's not painful. I looked it up; some websites say that it's a symptom of cancer, other websites say that it's a pigmentation (hyperpigmentation). What are some possible causes to this? Is there any treatment or anything I can do to? Thank you very much.