Pink for Owen Corning's insulation is the classic example of a trademarked color. Though if memory serves me correctly, there have been attempts to trademark colors later in time that didn't fare well. I think pink insulation was so different, unusual and well advertised at the time that it had transcended merely being descriptive (blue for a boating company) and there was a strong customer association between pink insulation and owen corning. As for a trademark without association to an item or logo - that would be difficult for anything because trademarks are registered because of their association with the provision of goods and services. The only way I can think of at the moment that you could pull something off like that is with made up words - like Google.
You need to understand that the color itself can never be trademarked, its impossible, check the trademark agencies if you want. Its pretty easy really, you can trademark the word pink http://tess2.uspto.gov/bin/showfield?f=doc&state=dmtu2i.2.6 but you can't trademark a colour unless its attached to a word or style/mark. No need to go around in circles.