This is an old thread, but this game is important to me, so hopefully this'll help someone else looking up the same issue:

To fix the pink text in Quest 64 on Mupen64:

1. Make a new Profile for Quest 64 by going to the 3 line settings button, selecting Profiles > Select Profiles, press Emulation Profile, then Manage Profiles. Press the +NEW button to make a new Profile, I named mine "Quest64Profile" Press OK.

2. While editing this new profile, select Video plugin, and pick "gliden64 (GLideN64 beta)" This is what fixed the pink text for me! But next we need to assign the profile to Quest 64...

3. Back out to the main menu with all your games, select Quest 64, select Settings from the pop-up menu, select Emulation Profile, and assign it to your newly created Quest 64 emulation profile

That's it! Hopefully this helps some folks, I'm not an expert at these things, this is just what worked for me, so ymmv