Thanks. But it looks like in all my frustration, I wasn't  sure  my original call for help had posted, so must have  submitted the same question again.

But I just had a new thought on the problem. While reviewing a story I received from another website,  I noticed that the photos attached to the article  looked  a lot like  what I described  in my  message. It made me wonder if I have a software problem at all . . . or if it's the screen on my Mac that needs recalibration!

It only took 2 minutes to find a website that discussed it — with sample screens to help determine if that was what I'm dealing with. Since a screen supposedly showing a mix of numbered, grey boxes looked totally white to me and I could only see the white numbers on a screen that supposedly contained boxes in varying shades of black, I think I might be on the right track. Just not sure, since I had to reach the bottom of the page before spotting the pitch for a product that supposedly will recalibrate  for me. I'm not sure I want to tackle recalibration on my own, but may call the Mac Geniuses at our local mall  and see  if my hunch is right . . .and if so, what they would charge to do it for me.

BTW, if it sounds like a calibration problem, do you think moving my computer  from one desk top another (just 5 feet away) could have caused it? I'm not sure, since it wasn't on my mind at the time, but I think that's roughly when I first started to notice discrepancies in color.

PS: I just skimmed thru that article you recommended. Haven't  digested the whole thing  yet, but can already see that I probably hit the nail on the head myself. Those photos midway down the page are exactly what you would have seen if I had been able to capture a screenshot.(i.e., mostly red and yellow images with dark blue and black shadows).

Thanks for your help in confirming the probable source of my  problems.!!