Content based image retrieval techniques are being developed for automatic indexing and retrieval of images in many applications. One of the main features of an image is its dominant colors, hence the development of color based image retrieval techniques. In these techniques, images are indexed using their dominant colors and images with perceptually similar dominant colors to the query are retrieved. In a large image database, images may come from many different sources, may be captured using different devices and represented using different color spaces. These differences may be subtle, but result in different meanings of image data. If these differences are not accounted for, image retrieval performance may suffer. In existing systems, this factor is normally not considered. In this paper, we present various different image representations. We then discuss effects on retrieval performance using color histograms when images in a database are represented differently. It is shown that different image representations have serious effects on image retrieval performance. We discuss the conversion between different image representations, and information required to carry out these conversions. This information is normally not available in most current image formats, which indicates a need of a common color image interchange format.