There are various methods of gray conversion of RGB color images. They are calculated by three functions, Grayscale function, the Desaturate function, and the value component of the HSV option of the Decompose function. By converting this method we found the gray color image but when trying the reverse it is not same as actual images. That is due to the function that produces same value for different color and when reversing there is conflict between choosing one of them. Here I want to introduce a function using Classification method that produces different values of gray color for a range of RGB color images so the nearly reverse is possible.