Help me with my NPC?

I need a script that allows NPC to attack players on one team, but deal no damage to players on another team. Heres what I tried: (combination of sword script and teamkilling script

local Player = game.Players:GetPlayerFromCharacter(hit.Parent)
humanoid = workspace.DroolingZombie 
Darkgreen = game.teams.Undead
if Player.TeamColor ~= Darkgreen then
	tagHumanoid(humanoid)
    humanoid:TakeDamage(0)
    wait(1)
    untagHumanoid(humanoid)
end
function tagHumanoid(humanoid, player)
	local creator_tag = Instance.new("ObjectValue")
	creator_tag.Value = player
	creator_tag.Name = "creator"
	creator_tag.Parent = humanoid
end
function untagHumanoid(humanoid)
	if humanoid ~= nil then
		local tag = humanoid:findFirstChild("creator")
		if tag ~= nil then
			tag.Parent = nil
		end
	end
end

I'm new to coding, so this is my first try. Help?