A novel method for color image segmentation is proposed in this paper. The method is based on the segmentation of each color plane independently using a watershed based thresholding of the plane histograms. The segmentation maps obtained for each color plane are fused together according to a fusion operator taking into account a concordance of the labels of each segmentation map. This operator produces a fused segmentation map containing labeled and unlabeled pixels which is used as an image of seeds for a region growing method : the color watershed. The color watershed produces the final segmentation of the initial image. This segmentation scheme is experimented using several types of medical images and results in a fast and robust segmentation.