How to differentiate two images?

I have a problem to differentiate two images. Two colour images is slightly different. I have to name both of the image as A and B because this image will be used as a reference for the next test. i have attached together both of the image.

and

Answer 1

[KALYAN ACHARJYA]

%Image A and Image B
%convert to gray Image
K=imsub(A,B);
If K=0 
both are same image 
else 
different image