distance between centroid and each pixel in the image.

I want to find the color difference in an object. ie Apple has almost red color .suppose if an object contains red and other colors also. Can i find the distance between centroid and each pixel. so by finding the min and max difference (distance) to recognize the object.Help me

[Adam]

What are you asking exactly? If you have a centroid value then yes, this is trivial, depending how you choose to calculate distance in colour space. If you don't yet have a centroid then that is something of a different question the what your title says.