There was an article in the Evening Standard about it roughly two to three years ago. (I don't know if the ever resourceful James Hatts can locate it.) But if I remember correctly it was a young architect working for something like the LEB, LT or GLC who decided to make a pretty straightforward commission, for something like a Tube electricity sub-station, interesting. He was interviewed by the ES and I think was still a jobbing architect. But nice building, and certainly much better than most of what surrounds. Perhaps he can be asked to do something for the Elephant Links project.
Incidently a friend claims her friend was asked to jazz up the Elephant shopping centre some years ago, and yes that colour pink (thankfully now replaced by the red-nose red) was taken from her favourite nail varnish.
Maybe another urban myth like the dead rat that was supposed to have been found floating in the, now-closed, Elephant swimming pool.
I heard that a young local girl won a blue peter award to light up a public building of their choice. She chose the aluminum sub-station housing building and that is the reason it changes colour at night time.
Dont know the origins of the building, but Jamie is definitely right about the blue peter award. The girl was the younger sister of someone I went to English Martyrs Primary (Flint Street,Walworth) with.
I'm sure Blue Peter filmed something there at the time - maybe someone at the BBC could tell you more?