I just bought a 2015 S and noticed this on my front bumper and my cat is black but the front fog light is blue looking.

 

That is a JCW bumper with fogs added.
An S bumper has round openings, and no "Escutcheon"

BTW: My cat is black and white!!

Anyway, this is an S bumper

 

Faded. Mine got replaced under warrant,y as well as the bumper a couple of years ago. You may try the dealer.

 

It's an S with JCW package sorry and I'm getting the JCW tune put on the car I will ask about the bumper

 

The foglight surround on the S with JCW aero pack is not painted. Its gloss black injection molded plastic.

Here is an old tsb for shadowline trim BMW's. They also turned a purplish color with age or exposure to certain chemicals.

SI B 51 53 02
Body EquipmentSeptember 2006
Technical Service
This Service Information Bulletin This Service Information bulletin supersedes S.I. B51 53 02 dated October 2002.designates changes to this revision

SUBJECT
Discoloration of Shadowline Trim

MODEL
E46 (3 Series), E60, E61 (5 Series), E64 (6 Series), E65, E66 (7 Series), E83 (X3), E53 ( X5) Equipped with Shadowline exterior trim

SITUATION
The optional glossy black Shadowline exterior trim may become discolored.

CAUSE
Analysis has determined that the discoloration is due to a film deposited on the trim which distorts the light reflecting off the trim. These deposits may come from car washes, hard water, or other environmental conditions.

CORRECTION
Deposits that cause the discoloration can be easily removed by polishing with a quality swirl removing polish, such as Meguiars #9.

Note: The glossy black trim pieces are anodized, not painted, and the discoloration does not mean that the surface has been damaged. Therefore, the trim pieces should not be replaced for this complaint.

 

2006? This is a F56 problem and the dealers are aware of it. SA said it was reacting to UV and the plastic formula was changed.

 

I used that TSB as an example of the recurring issue of discoloring trim issues within BMW. These issues or similar trim issues have been going on with black trim since the early 2000's.

The part is $35... in the end if the discoloration bothers you its a simple somewhat inexpensive fix.