Ron,
Good theory. The different (and quicker) wear of the blue is visible on my 1913 KNIL and 1917 DWM LP08, so I'm a 'believer' when it comes to side plate discoloration.
Here they are side by side (please ignore the VoPo grips, they're for handling purposes only):
It also helps to repeat the VoPo grip tip for owners of grip safety shooters:
The grips are hollow and are ideal for a grip safety conversion.