<p>My thanks for all the responses. I opened my attached file on a MacBook Pro. It looks gray around the edges. I found the digital color meter in the Utilities folder (thanks, Peter Mounier!), and checked the RGB values around the edge, and they do indeed vary among several gray values.<br /><br />There's something odd going on with the color settings on my Windows 8.1 computer. I'm looking into a color calibration tool such as DisplayMate. I don't trust the eyeball accuracy of Windows' Display Calibration tool -- and its settings don't "stick," either!<br /><br />I've avoided doing any color correction on my photos because I don't trust the environment.<br /> Thanks again, folks!</p>