I may bring it up, but I wouldn't dwell on it.

People go tanning, why should bleaching be any different?

If he was going through a "skin rejuvination process" perhaps the lightening was unintentional.

Well, I would likely comment on the difference in shade. However, my main reaction to his different coloration would likely be based on his feelings about the color. If he underwent skin rejuvenation, he likely had no intention of changing his color but is now simply facing one of the side effects of this process. Since skin color is by the individual person oftentimes regarded as a huge part of that person’s identity (since it is connected with culture and heritage), Sosa could be unhappy with the outcome and may need support in learning how to cope with his new color, if the color change is permanent. In terms of being my friend, I don’t see how a lighter skin color would make a great difference as to the person he is or has always been. Our friendship would likely be based on a mutual understanding and favorable personalities, rather than skin color. A new “shade” would not change my feelings towards him in any way. If I thought the change of color to his skin was intentional, then yes, I would try to find out why he decided to lighten up his skin. Was he feeling any type of discrimination? Or was he just simply unhappy with his previous coloration? However, this does not seem to be the case and so I think I would just try to find out how he feels about his lighter skin, that appears to have been the result of his skin rejuvenation. If he feels just as happy with it was when he was darker, and if he does not have any regrets, then why should I feel any differently?