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