Im using the script below and it works just find other then that the players dont actually spawn on the correct teams spawn. From testing it, it just choses a random spawn and spawns the player there. Does anybody know why and how to fix it?

local plr = game.Players.LocalPlayer
_G.teamNumber1 = 0
_G.teamNumber2 = 0
local team1 = BrickColor.new('Bright blue')
local team2 = BrickColor.new('Bright red')

function Set()
if _G.teamNumber1 > _G.teamNumber2 then
plr.TeamColor = team2
_G.teamNumber2 = _G.teamNumber2 + 1
elseif
_G.teamNumber1 < _G.teamNumber2 then
plr.TeamColor = team1
_G.teamNumber1 = _G.teamNumber1 + 1
elseif
_G.teamNumber1 == _G.teamNumber2 then
--do math.random or watever u like, I'll just put him to Team1
plr.TeamColor = team1
_G.teamNumber1 = _G.teamNumber1 + 1
end
plr.Neutral = false
end

script.Parent.MouseButton1Click:connect(function()
Set()
plr:LoadCharacter()
end)

Your Problem

What you have should work for spawning on a team's spawn. You should check that the TeamColor (and not just BrickColor) is set on the SpawnLocations, and also that Neutral is false on the SpawnLocation.

Fixing _G

The way you're using _G won't be useful.

_G is local to each client, so the numbers will pretty much always be 0 (even if they weren't local, each time a player spawns you're setting everything back to 0!)

Instead of trying to keep track of changes, just go ahead and count players by their teamcolor whenever you need them.

Here's a teamSize function I just wrote which looks through all players and looks at their Neutral and TeamColor properties, giving a count:

function teamSize(team)
	local players = game.Players:GetPlayers()
	local count = 0
	if team then
		-- Count not neutral
		for _, player in pairs(players) do
			if not player.Neutral and player.TeamColor == team then
				count = count + 1
			end
		end
	else
		-- Count neutral
		for _, player in pairs(players) do
			if player.Neutral then
				count = count + 1
			end
		end
	end
	return count
end

Now instead of reading the global variables, you just ask for the team size of the two teams.

local LocalPlayer = game.Players.LocalPlayer

local team1 = BrickColor.new("Bright blue")
local team2 = BrickColor.new("Bright red")

function Set()
	local size1 = teamSize(team1)
	local size2 = teamSize(team2)
	if size1 < size2 then
		LocalPlayer.TeamColor = team1
	elseif size2 < size1 then
		LocalPlayer.TeamColor = team2
	else
		-- Or randomly
		LocalPlayer.TeamColor = team1
	end
	LocalPlayer.Neutral = false
end