A little update: I tried "refreshing" the equipment (unequipping it, then equipping it after delay) about 15-30 seconds after the game is running. No dice.
Here's where it gets strange: When I recruit the character, either as a follower or a party member, then when the equipment refreshes, it displays correctly (the mask is visible, and the armor is the correct color).
So it seems that if the character is in "NPC" mode, the mask and the armor colors refuse to display correctly.
Additionally, if the character is added to the party and gets pulled into combat, the mask then displays correctly (the armor color stays the same incorrect default color). If the character is an NPC and pulled into combat, the mask remains invisible.
Oh, and for all of these tests, the character in question is standing right next to a player.
