Halo and TF2 (honestly forgot about that one for a hot second) are the only ones I can currently recall having Red vs Blue for matchmaking. But I largely play PvE games, and the PvP games I DO play don't have Red vs Blue as their team identifiers. Destiny (when I played it) didn't, the CoD games I've played don't have it, GoW doesn't have it, Battlefield didn't have it, Warframe's PvP mode doesn't have it from what I recall, Overwatch has a Red vs Blue system, but you're not forced to be red or blue, they do an outline system, Rainbow Six Siege didn't have it either.
I mean, being one color or the other hasn't stopped team mates from shooting one another, so look at the bright side, they now have an excuse as to why they're shooting you!you can only think of halo as red vs blue? so you havent played any original team game? or maybe TF2.
Honestly, as someone who got super confused on who was friend or foe in Warframe like 7 years ago, I can confidently say it's something that will grow on you. Yes it's not what Halo has done for 20 years. Yes it's different. No it's not the end of the world. Just gotta get used to it, we got used to armor abilities instead of armor equipment, didn't we? Now we have to readjust to a sort of mix of armor equipment and armor ability.
Edit: Actually thinking on it now, Halo is the only game I can think of that ever did Red vs Blue. Gears of War was always human versus Locust, CoD didn't do Red vs Blue either, even back in the day. Has any other game actually ever done Red vs Blue visually???
for honor does RvB as well as rocket league and both of those game have a cool system where you can change to different shades of red or blue so you arent all the same but its still red and blue. half life 2 deathmatch did RvB as well as the old quake games if i recall.
red vs blue is a widely used system that mainly exist in arena games but not so much in other games except maybe RTS's age of empires uses team colors aswell i think.
destiny and cod arent really arena shooters in the classic sense like halo is, I dont play GoW so i dont know what type of game it is. games like siege, LOL, over watch, dota, and what not are hero based games those dont normally have team colors for characters. and battlefield has always been its own thing wanting to put emphasis more on country armies then just colored teams.
I think this is just one of those cases where since you honestly dont seem to play the type of games a RvB color would exist in you just didnt know, but yeah these days most people play games where you play as a character instead of a colored man so its easy to forget that it used to be the system for team games.