The code can only be solved with two images, a code and a key. Luckily for you, in this case I included both the code and the key in this one image.
The top and the bottom halves of the image are almost identical, with a few pixels different. If you lay the halves on top of each other and color each point where they differ black, you will get the message
"ENJOY 'PLEXUS PROBLEMS DAILY!" |