Here is the answer:
First, you need to put a BoolValue in the ServerStorage (or anywhere)
Then, Place a Part containing a ClickDetector.
Next, you will have to write the script in a ServerScript inside the clickable part:
1 | local Value = game.ServerStorage.Value |
2 | local function clicked() |
6 | script.Parent.ClickDetector.MouseClick:connect(clicked) |
After, you write this in a LocalScript that is placed inside StarterPlayerScripts:
1 | local Value = game.ServerStorage.Value |
2 | Value.Changed:connect( function () |
3 | _G.Gui.TextColor 3 = Color 3. fromRGB( 0 , 0 , 0 ) |
4 | _G.Gui.Font = Enum.Font.Cartoon |
Lastly, because without this script it will throw an error, write this in a LocalScript inside the ScreenGui:
1 | _G.Gui = script.Parent.TextLabel |
There ya have it ;)
It's a little complex because of the way Roblox Lua throws errors at you, but it's good to know how it works!
Also if the you do not click a part, but a Gui button then please comment "Wrong Click" for me to explain that side, which is way easier :D