Returns the NSColor object associated with the given key.
Original signature is '- (NSColor *)colorWithKey:(NSString *)key'
Available in Mac OS X v10.0 and later.


- key (NSString)
- The key for which to retrieve the color.

The color associated with the given key or nil if there is none.

- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)