What is a chromatic artifiact?
Look at the AP scan of the image and blow up one of the letters extremely large and look at the edges of them (where the letters end and the background begins) and you will see blue and redish haze around the entire letter or area that goes from black to white. From what I understand of the subject this is due to the way light passes through a lens of a scanner and present in EVERY color scan. It is present in the AP version because they actually scanned the document with a color scanner.
Look at the pdf released by the WH and do the same thing, there are no chromatic artifacts present at all.