Snazzy Maps is a repository of different themes for Google Maps aimed at web designers and developers. All the themes on the site are free to use under the creative commons license.
As of version 3, Google Maps API now allows custom styles that can be applied to maps. This allows developers and designers pick and choose the theme that matches their site.
Snazzy Maps is the best free resource for different color schemes that can be used for Google Maps. Check out Snazzy Maps HERE