It's all about reasonable expectation. Can a person reasonably be expected to think that a light blue packet would contain Equal? If yes, then Equal can copyright the light blue packet for use in their sweeteners. Can a person reasonably be expected to know that Red Bull has a specific shade of red and blue? Can a person reasonably be expected to know that an all red can with a swoop on it should contain Coca Cola and should it be resonably expected that if a person saw a can that wasn't coke but was red with the swoop that they would confuse it with a can of Coca Cola? If the answer is yes to the last question, then Coke can have a copyright. even though it's just a color and a swoop, which isn't even really a logo.