I was just browsing images last night as I had nothing else to do (what an original excuse

) and noticed a picture of 142002 -
Original:
http://www.53a-pix.co.uk/picture/142002-MV-280600.jpg
Recently (majority is now black):
http://www.railfaneurope.net/pix/gb/...Central-01.jpg
Now: Now it's sporting a far brighter yellow than in the second picture above.
I was just wondering what reasons could there be for changing the front end of a train?
I'm all very new to being somewhat of a rail enthusiast so please excuse me if i've got all this wrong, i'm just being curious.