The shield colour in current Infinite Tech Preview is based off of your own chosen colour for the friendly, enemies and fireteam member, however, I think it should be a seprated option.
For example, I like having red colour for the enemy and green for friendly but I could want to have yellow shield for all or even have a entirely different shield colour for myself, teammate, fireteam and enemy.
Add the shield colour option for my own, friendly, enemies and fireteam please 
BONUS: The shield regeneration animation from your first person percetive should have the colour changed depends on the shield colour you have, it’s really strange seeing my own green shield and still have yellow tint when my shield regenerates