A few people have seen the invincible supports vanish, and someone theorized it was because of a bug in the color-changing that lets them change to loyalty on occasion. In Warlords’ Stand I just saw proof that they were right. The AI successfully matched the invisible support with loyalty gems (in a match-5 no less) and it changed back to a color, though I don’t remember which as several cascades followed.
//Edited Title -Brigby