KJS
Member
Clearly not a very important question, just something that's always seemed odd.
I remember the deep blue of the Colts I've had.
When they invented a new chemical formula for controlled corrosion they wanted a new name. It looked different and was kind of blue black so they called it 'bluing'. They probably wouldn't want to call it 'blacking' because that term was already in use for some kind of black polish one put on cast iron stoves and the like.