How do I make it so one of the roblox teams vision is blurred or foggy?

I am NOT a good Lua coder, but I can give a simple suggestion as to something that may or may not work. You could add a local script that checks for when the local players character is loaded. When that player is loaded you can have an if statement checking which team they are in, and within that if statement have a code that accesses the blur effect (that you add into lighting). Since it is a local script I am pretty sure only that local player will view it.

So

--when local player character is loaded
--if that local player is a part of the team you want blurred
  --change the blur size to the amount of blur you want

I don't know the exact syntax of this, but hopefully this helps

This is my guess, not sure cuz never used blur on my games. If this doesn't work then the problem is on line 1

local Player = game.Players.PlayerAdded
local Team = game:GetService("Teams")["No Team"]

game.Players.PlayerAdded:Connect(function(Player)
    if Player.Team == Team then --Change
        game.Lighting.Blur.Enabled = true
    end
end)

This May Not Be How You Wanted It But I Know A Script That Kinda Does What You Want First Of All You Can Do This Script

Game.Players:ClearAllChildren()

OR You Can Do This

local GUI = game:GetService("StarterGui")
-- gets the UI Core,Gets The Ui Type      -- Set The Ui To Be Invisible
GUI:GetCoreGuiEnabled(Enum.CoreGuiType.PlayerList,false)