I plugged in the charger of my laptop into a socket, which I have done a lot of times but this time, I noticed a strange thing. When the contact was made between the pins of charger and the socket, there were sparks at both pins but one of them was orange and the had a blue shade. What causes the colors and why are they different for both the pins.
An electrical spark will vapourise part of the surface where it is generated. With a large spark this can cause visible pitting, though if the spark is small you may only be able to see the damage under a microscope.
Anyhow, just as in a flame metal ions present in the vapour can be excited by collisions and then decay to emit light. The colour of the light emitted will depend on what atoms are present in the flame and at what concentrations.
The trouble is I can't make any further comment because I can't inspect your plug and socket to see what might be causing the difference. I'd be surprised if the pins on the plug were made of different metals, but they might be corroded to a different extent and it could be metal atoms from the corrosion that are responsible. Alternatively it could be that different levels of corrosion mean the sparks are bigger and hotter on one pin than the other. Finally, the difference could be due to the contacts in the wall socket rather than on the plug.