I think it's possible to change individually
The colors of the outlines are saved in the LVL KWNs
https://media1.tenor.com/images/1ab473c59919580e9f467e8d9b5b9760/tenor.gif
You can basically change their alpha
@AdrienTD Are the flags textures located inside GAME.KWN? I was wondering if we will be able to not only modify them, but also to get more if we need...
They are in the LLOC files, for each level.
Which means you would have to change the flag for every level
Oof. I wonder then, what would it show for a 6th language, granted we edited the 6 GLOCs to acknowledge its existence