[Feature Request] Add Color When Playing as TANK option for friendly tank-like NPCs

[10hendersonm]

What

• Add an option to the Colors / Threat > Color When Playing as TANK section called Aggro on Another Tank (NPC) or something similar.
  Photoshop mock-up:
  
• Default the color to Aggro on Another Tank
• Color applies when mobs are aggressed to units like this non-exhaustive list
  • Earth Elemental
  • Do druids still have treants?
  • Monk black ox statue?
  • Maybe Tenacity hunter pets

Why

I get scared whenever somebody throws out an Earth Elemental because the plates all go red and I assume one of my DPS has just popped off and is about to die.