Image processing is carried out in general with monochromatic information. Therefore, it does not consider the color information of the objects. However, the human visual system is very sensitive to the color information, so it seems logical to introduce this information to increase the capacity of computer-based systems. Obtaining all the spectral information for each pixel of an image could be very expensive but the image acquisition systems may provide several images each one corresponding to a spectral sub-band. In this paper, we introduce the color as the third dimension of images and extend the definition of Fourier transform and correlation to these signals. Firstly, we study the Fourier transform properties of these three-dimensional images, paying special attention to the third dimension, which contains the color information. Then, the correlation operation is studied. As an application, we extent the pattern recognition method based in correlation to these signals and we show the advantages of introducing the color information.