Why is my simple admin checking script with a bindable function not working?

So this is a simple script where a player steps on a brick and it checks to see if it is an admin or not. If the player is not an admin, they die. If the player is, the brick turns yellow. I wrote the script corresponding to a scripting tutorial: https://www.youtube.com/watch?v=jQ0iClyt_zA&t=312s

Here is the script with the bindable function and list of admins:

admins = {"crystalclay", "Player1", "Player2", "John", "Bob"}

script.GetList.OnInvoke = function(name)
	isAdmin = false
	for i,v in pairs (admins) do
		if name == v then 
			isAdmin = true
			break
		end
	end
	if isAdmin == true then 
		return true
	else
		return false
	end
end

The problem with this script is that, on line 4, the first "isAdmin" is underlined in blue.

Here is the script for the part:

script.Parent.Touched:connect(function(hit)
	 humanoid = hit.Parent:FindFirstChild("Humanoid") -- The first "humanoid" is underlined in blue
	if humanoid then 
		 playerName = hit.Parent.Name -- "playerName" is underlined in blue
		isAdmin = game.Workspace.ListoAdmins.GetList:Invoke(playerName) -- "isAdmin" is underlined in blue
		if isAdmin == true then 
			Part.BrickColor = BrickColor.new("Bright Yellow") --"Part" is underlined in blue
		else
			humanoid.Health = 0
			
		end
	end
end)

I do not understand why there are blue underlines as I double checked and typed the script exactly as Peaspod did in this video.

Here is the error message I'm getting: 21:51:31.537 - Workspace.Part.Script:7: attempt to index global 'Part' (a nil value)