In 1957, as television broadcasts became commonplace, the NFL instituted a rule requiring teams to have light-colored jerseys for road trips. Before then, it was not uncommon for both teams to take to the field wearing the same color. Throughout the Packers' history to that point, it was most common to see this kind of "color clash" with the Bears, navy jersey against navy jersey. A different color clash occured in early December 1952 when the Packers journeyed to Los Angeles to take on the Rams.
As we've seen, the Packers often wore gold jerseys during the Gene Ronzani era of the early 1950s. The Los Angeles Rams also wore gold jerseys during this period, as seen on this picture of Crazylegs Hirsch, from his 1956 Topps card.
For the game at the Coliseum on December 7th, both teams wore their gold jerseys. LA coach Hampton Pool, not happy about the clash, played the game under protest. From newspaper coverage of the time, you can see how easily this would become confusing:
Pool needn't have bothered with his protest - the Rams won handily, 45-27.
(h/t: Timmy B)