White Knights

In 1938, the Packers introduced their first white jersey, an alternate designed to avoid a "color clash" when the Packers faced the Bears, Cleveland Rams or other blue-clad squads. The white jersey with green numbers was worn with white socks and the Packers' standard gold helmets and pants.

Packers quarterback Cecil Isbell models the team's first white jersey

Clarke Hinkle in a 1938 promotional wire photo (reverse here)

This uniform would form the basis of the 2001 Thanksgiving Day throwbacks.

Ahman Green rushes for a touchdown in Detroit

There don't appear to have been any hard and fast rules about the circumstances under which the alternate was worn, given the number of navy-on-navy matchups the Packers played against the Bears. Perhaps Curly Lambeau, knowing how they irritated George Halas, just liked tweaking his nose.