Abstract. One main process in Computer Vision is image segmentation as a tool to other visual tasks. Although there are many approaches to grey scale image segmentation, nowadays most of the digital images are colour images. This paper introduces a new method for colour image segmentation. We focus our work on a topological study of colour distribution, e.g., image histogram. We argue that this point of view bring us the possibility to find dominant colours by preserving the spatial coherence of the histogram. To achieve it, we find and extract ridges of the colour distribution and assign a unique colour at every ridge as a representative colour of an interest region. This method seems to be not affected by shadows in a wide range of tested images.