Coloration of fuselage during aircraft construction ?

[Speedbird1]

I was always curious about why a bare metal aircraft fuselage during construction appears as a light green or blue color. If the fuselage skin is usually aluminum, wouldn't the skin appear a shiny silver rather than green or blue? Is this due to a chemical reaction of some sort? Boeing will not discuss their manufacturing process with the public.

[heeshung]

It's primer, usually some version of zinc chromate.

[Speedbird1]

Thanks for the info. Is this related to the process called "Pickling" often used on metallic surfaces to strengthen them?

[Ari707]

usual the only part that is painted during construction is the rudder, so it can be balanced when it is installed.