The only other thing that could cause the silkscreen to be not as bright, or at a lower intensity, compared to everything else is that the Silkscreen was previously exported as a design partition and never re-imported into the master design. Team Design (Design Partitioning) is not an available option with OrCAD PCB Designer 16.6 but maybe in 16.5 someone had access to an Allegro PCB Designer license w/Team Design option that may have enabled the export.
If this is the case you would not be able to move the silkscreen text around at all as it would be locked, or in read only mode, after the partition was exported. Are you able to move the silkscreen text in OrCAD PCB Designer 16.6?
Maybe something in the database was set to make it think a partition was exported but in reality it was not exported. You could try changing the environmental variable DISPLAY_READONLY_INTENSITY to 100 and see if the silkscreen items are displayed like normal. (Setup > User Preferences under the Display Category / Visual folder.)
Of course it is a long shot that this is the case but I had to bring it up.
Hope this helps,