Install imagemagick. You can then create a list of every pixel in an image using something like:
convert foo.jpg foo.txt
The text file will contain every pixel in your image, 1 pixel per line:
0,0: (230,232,229) #E6E8E5 rgb(230,232,229) 1,0: (230,232,229) #E6E8E5 rgb(230,232,229) 2,0: (230,232,229) #E6E8E5 rgb(230,232,229) etc
If you want to find a single color, try:
FINDSTR E6E8E5 foo.txt > lightgrey.txt
to dump a file of every pixel containing the color E6E8E5
. You can search for the rgb part of the line too, if you'd rather.