Long story short, the answer is fairly sensible: you can't own a color per se, but you can trademark a color associated with your company for use against competitors the same way you can trademark any other imagery or words.
So, for example, I can use Cadbury purple to paint my car, or to as the color of my book store, etc., but if I try to use it selling candy, I might very well get a cease-and-desist order from the Cadbury lawyers, for fear that I might cause confusion as to whether I'm an official Cadbury candy or not.
Makes sense, remarkably enough. More sense than a lot of other related intellectual property law. #ddtb
Embedded Link
Can you own a color?
From Cadbury's purple to UPS' brown, companies understand the power of purchasing a particular hue
Well, it makes a lot of sense, especially since people tend to not pay attention to writing on packaging. Did you hear about the Coke fiasco with changing their can colors and people bitched that they thought it was Diet Coke…dude…read the label! lol
Color is a great at-a-glance identifier for humans. A reason why changing your company colors is a dangerous action.