I have two cocobolo pens I use daily at school. One of them was stolen last year from the fair and the mother of the boy that took it found it after it had run through the washer! Anyway, went and looked, the one that went through the washer is darker, but it also had leaked its ink during the wash. It is possible, I used the light/white Hut friction polish on them. Being in my pocket they aren't laying around in light/daylight situations. So my guess and it is a guess only, depends on how it is used/where it is stored/displayed. With daily use, some darkening but that is probably dirt. Sorry no real help here. Cocobolo sure is a pretty wood to work with, it is one that bothers some people. Good luck and hope someone steps up and gives you a definitive answer.