Your photograph doesn’t appear to correspond with a genuine first or second generation Apple Pencil - but perhaps instead a third-party stylus of some other origin.
A first generation Pencil has a removable cap - beneath which is a Lightning connector for pairing and charging the Pencil. A genuine second generation Pencil is a sealed single-piece housing - whereas your photo clearly shows a visible seam around the end-cap that has changed colour.
Genuine Apple Pencil tips are off-white/light-grey in colour.
While the colour change is very likely to just be cosmetic, should you have any concern, you’ll need to seek assistance from the retailer from which the stylus was purchased - or its manufacturer.
If the Pencil is a genuine generation Pencil, you would be well advised to seek assistance from the Genius Bar at your local Apple Store - where the technicians will be able to assess the Pencil for defects:
Genius Bar Reservation and Apple Support Options - Apple