luau How do i make it so it show up to other players?

Solution

You can use a RemoteEvent. For this one the RemoteEvent should be in ReplicatedStorage and named PoliceLights. Create a normal script in ServerScriptService as well.

What is a RemoteEvent?

If you don't know what RemoteEvents are, they are used to send data Client-Server and vice versa. The Server is the game itself and the Client is the player themself. Normal Scripts run in the Server while LocalScripts and Normal Scripts that their RunContext is set to Client run in the Client. If something is changed in the Server, it will also show up in all Clients, while if something is changed in one Client, it will only show in that Client. RemoteEvents crosses that boundary and makes it that if you want to change something in the Server in a Client script and vice versa, you can actually achieve it.

Tips & Extra Solutions

Tip: You don't need to connect UserInputService.InputBegan twice to make two parts change at the same time, you can use task.spawn() to make them run at the same time.

Tip 2: If you press E multiple times, it might glitch the two parts. To fix that, we will use a debounce in which we will wait for the two parts to finish glowing before pressing E again.

Tip 3: If you type E in the chat, it will activate the two parts, we will use the second parameter of UserInputService.InputBegan's callback function gameProcessedEvent which is a boolean (true/false) that tells if it was processed by the game (e.g., typing E in the chat or in a TextBox), and check if it's true, and if it is, we will immediately stop the callback function using return.

Tip 4: Use task.wait() instead of wait().

Final Script

Normal Script in ServerScriptService:

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage.PoliceLights

local goodpart1 = workspace.transporterT4.Body.biglightbar.unionright
local goodpart2 = workspace.transporterT4.Body.leftlightbar.main

local pressedE = false -- this will be our debounce
RemoteEvent.OnServerEvent:Connect(function() -- this callback function will run if RemoteEvent:FireServer() in the Client successfully reached the Server
    if pressedE == false then -- if E hasn't been pressed yet
        pressedE = true -- it will tell that E has been pressed

        task.spawn(function()
            goodpart1.BrickColor = BrickColor.new("Medium blue")
            goodpart1.Material = Enum.Material.SmoothPlastic
            task.wait(0.15)
            goodpart1.Material = Enum.Material.Neon
            task.wait(0.15)
            goodpart1.Material = Enum.Material.SmoothPlastic
            task.wait(0.15)
            goodpart1.Material = Enum.Material.Neon
            task.wait(0.15)
            goodpart1.Material = Enum.Material.SmoothPlastic
            task.wait(0.15)
            goodpart1.Material = Enum.Material.Neon
            task.wait(0.15)
            goodpart1.Material = Enum.Material.SmoothPlastic
        end)

        goodpart2.BrickColor = BrickColor.new("Medium blue")
        goodpart2.Material = Enum.Material.Neon
        task.wait(0.15)
        goodpart2.Transparency = 0
        task.wait(0.15)
        goodpart2.Transparency = 1
        task.wait(0.15)
        goodpart2.Transparency = 0
        task.wait(0.15)
        goodpart2.Transparency = 1
        task.wait(0.15)
        goodpart2.Transparency = 0
        task.wait(0.15)
        goodpart2.Transparency = 1
        task.wait(0.15)
        goodpart2.Transparency = 0

        pressedE = false -- it will tell that E hasn't been pressed yet
    end
end)

LocalScript:

local key = game:GetService("UserInputService")

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage:WaitForChild("PoliceLights")

key.InputBegan:Connect(function(input, gameProcessedEvent)
    if gameProcessedEvent == true then return end

    if input.KeyCode == Enum.KeyCode.E then
        RemoteEvent:FireServer()
    end
end)