Abstract: We propose a method of image segmentation using a Gaussian mixture model of the colour image histogram. The model construction is based on the model validation philosophy of architecture selection [8]. In contrast with the k-means clustering approach, the number of segments in the proposed scheme is determined completely automatically. We show that the modelling method can be strengthened by incorporating spatial contextual information. The proposed approach speeds up the modelling process by a factor of three. The advocated methodology is successfully applied to the problem of lip pixel segmentation in face images.