MuseScore mystery: Default paper in Preferences > Canvas > Paper, allegedly paper5.png, is actually a different color?

Inspired by https://musescore.org/en/node/108386, I started investigating MuseScore's wallpapers. I found something deeply confusing.

If you go into MuseScore's Preferences and click on the Canvas tab, it looks by default like this:

Notice that under both the "Background" and "Paper" sections, the radio button for "Color" as opposed to "Wallpaper" is selected. But while under "Background" the other "Wallpaper" option is blank, under "Paper" it's pre-filled in with ":/data/paper5.png".

Now, if you click the radio button for "Wallpaper" under the "Paper" section, that PNG file is activated as the wallpaper, so it looks like this:

And if you click "OK," then MuseScore looks like this:

Now, go back into the Preferences, to the same place, and click the folder button to the right of "Wallpaper" under "Paper" to browse for a specific wallpaper. The default location opens up, with five wallpapers, paper1.png through paper5.png.

Choose paper5.png.

Bizarrely, this is a different color than the other paper5.png!

And when you click "OK":

I've been digging through the source, and I can't figure this out. They should both be coming from the same PNG file, https://github.com/musescore/MuseScore/blob/master/share/wallpaper/pape… . The last one seems to be correctly rendering the rather onionskin-looking PNG. But the one put into ":/data", the default, comes out different. Why? I'm deeply intrigued.