So I did some research. I have a Win7 environment still running older FCXE 777 and the selected file color is certainly the familiar pale blue I'm looking for.
Here is the Win10 "dark blue" example:

And for contrast here is the Win7 "pale blue" example:

NOTE: This is a Win10 environment using FCXE 787, and there is a custom desktop color scheme.So it may be the result of this Win10 color scheme that the selected file color is dark blue. If so, I'd like to know how I manually customize the selected file color to once again be the same pale blue as I'm accustomed to for all of these years. I don't see any Settings option which specifically sets the color of a selected file.