Your comparing water color Amano concept art to actual in-game icons? How absurd. If you ONLY referenced Amano art then you'd quickly realize that most if not all his art is colored differently than what actually happens. Okay I will admit I have no honest answer to Faris being a red dragoon, honestly I forgot about it, but 1 character out of how many were the traditional Purple to black color scheme? All the rest.

On the Tactics...YOU cannot get a red/green/blue color variants, I hate having to explain the obvious, but here we go.

You are taking a system style (Tactic battle system) and trying to warp its function to your betterment, what you fail to realize is that the ENTIRE ENEMY TEAM is also Red/Purple/Green/Blue/etc. Its a common function in Tactics based video games to better represent opposing units vs your own units. To provide you with proof to this claim you need look no further than the evidence you have provided, if you want additional proof then go open a copy of Star Craft 1 or 2 and play the multiplayer, you will quickly notice there are a set number of colors you can choose from to distinguish your own units from the enemy units.

Its a shame that you have resolved to use "parlor-tricks" so to speak to make a claim where you have none. I'm not being mean, I am being factual.