Build a Lab color model in opencv

Question

I need to create a color model based on the "a" and "b" channels of the Lab color space. I have successfully separated the three channels "L", "a" and "b" and I used this code to compute the mean and standard deviation for "a" and "b":

Scalar aMeanDev;
Scalar aStdDev;
meanStdDev(A, aMeanDev, aStdDev);
uchar aMean = aMeanDev.val[0];
uchar aStd = aStdDev.val[0];

Scalar bMeanDev;
Scalar bStdDev;
meanStdDev(B, bMeanDev, bStdDev);
uchar bMean = bMeanDev.val[0];
uchar bStd = bStdDev.val[0];

I really have no idea how to continue. The final output of this project would be to use the resulted color model for image segmentation.