Biologists have studied the Human body in incredible detail.  We have solved many puzzles of how our bodies work. Some things are still mysterious.  Nobody is sure quite how emotions, values, and faith are stored in the brain, or how they manifest in the body.  There is one thing, though, that has been well established.  Melanin content in the skin has no connection to emotions, values or faith. 

There has never been any case of someone's skin becoming lighter or darker because of changes in their personal values.  Nobody has ever changed color from getting religion.  Committing crimes does not change the color of anyone's skin.  Volunteering for charity work does not affect it.  Getting a tan will not make someone become violent.  Staying indoors and becoming very pale will not make someone smarter or kinder.  Insanity doesn't change one's complexion.  Skin color does not reflect ANYTHING about a person's intelligence, emotions, values or faith.

That is a fact.

In a culture that will not accept that, something does happen.  Someone with a different color of skin will have had a different experience in the culture.  So, they are likely to have a different outlook on life, perhaps even a sour one.  But, that's not because of melanin.  It's because of asshats.