Well you have to think of some way to split the boundaries. Since there is nothing that really indicates where to split it, you might have to do that manually. Use ginput(3) to have the user click on 3 points. Then zeros them out and then do this:
labeledImage = bwlabel(binaryImage, 8); % Label each blob so we can make measurements of it
coloredLabels = label2rgb (labeledImage, 'hsv', 'k', 'shuffle'); % pseudo random color labels
imshow(coloredLabels);
