Now you can restrict the results of Google Image Search based on their color. This option is not yet available in advanced search, But you can use for example, "imgcolor=green" as a parameter in the URL.

If you restrict the imgcolor parameter to green, you will get images which are mainly green in the results. For example search for apple and restrict the results to green, then you will see only green apples in the results.

Try this new feature by using this sample drop-down.

http://images.google.com/images?q=apple&imgcolor=green gives green apples as shown in the graphic below.

Thanks Ionut Alex for developing the sample dropdown and the information.