Color change of case

Kbatu

Estimable
Jul 17, 2014
5
0
4,510
Hello Tom's Hardware community. I have a Samsung NP300E3C model laptop. I decided to clean the dust inside the of my laptop. I opened the case and I saw that the bottom part which comes off has changed color from black to bronze with rainbowish endings(1. picture). The only piece which has the same color is shown in the 2. picture. Its the piece with the upside down U shape. My question is whats that piece and why did it changed color and the color of the case?
1: http://i.imgur.com/TJksk5L.jpg
2: http://i.imgur.com/5pjzFWl.jpg

Thank you for your time.
 
Solution
1) Copper covering, for radio interference protection. It's painted over on bits you might see.

2) Heat pipe. Conducts heat from the CPU to the heatsink, which the fan blows through. Outer layer is copper, because copper conducts heat well.

Kbatu

Estimable
Jul 17, 2014
5
0
4,510
So is it normal that there are rainbowish parts on it but not the whole copper?
EDIT: I mean the piece on 2. picture the metal piece looks like it changed color.