The rapid growth of image archives increases the need for efficient and fast tools that can retrieve and search through a large amount of visual data. In this paper, we propose an efficient method of extracting the image color content, which serves as an image digital signature, allowing us to efficiently index and retrieve the content of large, heterogeneous multimedia Internet based databases. We apply the proposed method for the retrieval of images from the WEBMUSEUM Internet database, containing a collection of fine art images and show that the new method of image color representation is robust to image distorsions caused by resizing and compression and can be incorporated into existing retrieval systems which exploit the information on color content in digital images.