To become altered or spoiled in color.
engines get discolored because of the heat . the heat comes from combustion from gass and air
The bracelate surface does not get discolored after usage. Rubbing with clean cotton cloth can bring back original shine, very easily.
Discolored spot on skin
No.
Same reason anything else turns discolored when they die. Their cells are dead and discolored.
You probably need to bath occassionally
dyed hide
Teeth get discolored from the food that you eat and the things that you drink. Almost everything you eat or drink is a color and over time that can stain your teeth, this is why brushing is so important.
oxygen
oxygen
probably a manufacturing issue
no