The color always shows when Elytra is equipped to chestplate slot but goes back to vanilla enchant glint when equipped to back slot (Curios)

Edit: Used rainbow colored rune, haven't tried with other colors
When on Curios back slot, the rune on Elytra shows when:

• Player is holding a tool with colored rune applied (sword, also rainbow in this case)
• Player is holding nothing (empty hands)

Otherwise, or if holding a tool with vanilla enchant/no colored rune, the Elytra goes back to vanilla glint

Not fixable without doing hacky mixin nonsense into other mod code, which we'd rather not do