Q: Problem with display in viewing my photos: I get red stains in different parts of the photos. Does anybody know how to fix this?  I restarted my MacBook Pro but it did not solve the problem.

Details please

What version of Aperture? Is OS X 10.7.5 as you state correct for your OS? Are you shooting JPEG or RAW? If RAW what camera? Whar ahs changed since this worked?

LN

Are the red stains solid blocks of red? Then check, if you accidentally enabled ""highlight hot and cold areas" in the view menu. Try to disable this setting.

if you are using Aperture  3.6, disable Onscreen Proofing in the View menu Or change the proofing profile.

You're welcome