Why won't this script that gives certain tools to a team work?

Line 4 is incorrect. You are using an incorrect operator, =, which should be ==. Also, you should practice better indentation, so the code is better to read like so:

function onRespawn(character,player)
teamColor = player.TeamColor
for _, a in pairs(game.Teams:GetChildren()) do
	if a.TeamColor == teamColor then
		teamColor = a
	end
end
if team == nil then return end
weps = game.Lighting.TeamsStarterpack:findFirstChild(team.Name)
if weps == nil then return end
	for _, a in pairs(weps:GetChildren()) do
		weps:clone().Parent = player.Backpack
	end
end
workspace.ChildAdded:connect(function(character) 
	player = game.Players:GetPlayerFromCharacter(character)
    if player ~= nil then onRespawn(character, player) end 
end)
player:Kill()
end