Can you trademark a color?

A color trademark would not prevent a company in a different field from utilizing that particular shade, but it does prevent the use of that color in a way that would create brand confusion.

For example, a clothing company would not have any problem using UPS’s particular shade of brown.  However, if another package delivery company started using the color brown to market and brand their services, that would likely result in an infringement of UPS's trademark rights to the color brown.

Examples of Trademarked Colors

1. UPS Brown

The famous UPS brown was originally "Pullman Brown". In a NYT interview, Peter Fredo explains:

''They started out being Pullman brown,'' said Peter Fredo, U.P.S.'s vice president for advertising and public relations, when I ask him about the history of the brown trucks. The trucks have been brown since 1916. ''The reason they picked up on Pullman,'' Mr. Fredo said, ''is that it was the epitome of luxury and class at the time.''

2. Tiffany Blue

As explained on the Tiffany & Co. website:

The color known as Tiffany Blue was selected by founder Charles Lewis Tiffany for the cover of Blue Book, Tiffany’s annual collection of exquisitely handcrafted jewels, first published in 1845. Also referred to as robin’s-egg blue or forget-me-not blue, this distinctive color may have been chosen because of the popularity of the turquoise gemstone in 19th-century jewelry. Turquoise was also a favorite of Victorian brides who gave their attendants a dove-shaped brooch of turquoise as a wedding day memento.

3. T-Mobile Magenta

T-Mobile has registered its trademark Magenta, which was upheld in a case against AT&T:

A squabble over who stole the magic marker seems more fitting for a classroom than a courtroom. But a federal judge has sided with T-Mobile in a recent trademark lawsuit, saying that Aio Wireless, an AT&T subsidiary, isn't allowed to use colors resembling T-Mobile's promotional "magenta" color.

The Texas court has ordered AT&T to stop using Pantone 676C, a.k.a "plum," over fears that it might cause consumers to confuse the two brands. According to the presiding judge, T-Mobile successfully argued that letting Aio continue to use a variant of magenta would cause it irreparable harm. (Source)

You can see more examples like these in our full article on trademarked colors.