you can use settings players alliance color green
Only if the group you're trying to mark whitelisted you then you may have the ability to mark its members, what do you think ?
I'm going to confirm with Nuko and edit this post if such thing is possible to develop.
Re-read the topic I don't think u got the idea.The idea here is to make it easier with identifying your enemy, In my case yesterday we had 0 groups in our alliance, but we had some friendly groups which were helping, and it was pretty much impossible for me to know who I am against.By highlighting I mean adding a layer of neon surrounding the enemy's ped.