What Causes Penis Skin And Shaft To Be Darker In Color?

hi. Im 31y/o, 165cm tALL, 60 KG, ATHLETIC BUILT, active. I'm circumcised and through the years, i notice my penis skin especially on the glans and the shaft are getting darker in colour. I also notice its getting a bit wrinkly when flaccid. is there any other ways to make it shine again? I mean naturally through food? I heard papaya is good for skin. can I apply it on my penis to make my penis return to its former colour i.e pinkish? tq.