I am dealing with someone who had a PDF created from an external source. When they get the file an image in the document is basically blue when it should be black. I get the same results on various different versions of reader 7, 8 and 9 on different OS. The only catch is that if I actually print the document the image color is correct.
Go to Edit, Preferences, Page Display and make sure the Rendering/Smooth Text is set to none. I have read this in a previous post as I had the same issue for my users. This seems to have corrected it. I noted in the posts that some had to change to at least 16 bit color in addition to the change.