I am converting color from RGB to CIELab to train a GMM. When I get back the mean of clusters of the GMM I have sometimes negatives values in RGB space. I was wondering if the mean of only visible color can be non visible color ? Therefore I was also wondering if the visual color of CIELab forms a convex shape.
EDIT: I'm using Expectation-Minimization of OpenCV to train the Gaussian Mixture Model.