AMC's The Walking Dead has been gradually decaying each season since the show started, according to the official website for Skybound Entertainment's The Walking Dead comics.
Each season it has changed subtly and become a little darker and more “golden” and more disintegrated. It’s very symbolic of the disintegration of the world.
WalkingDead.com have created an animated GIF that moves through the last five years of logo's. Check it out: