Rainbow GUI

Installation

Press Win + R
Paste this into the window that popped up: %appdata%/.minecraft/LabyMod-neo/addons and press enter
It should open your Labymod addon directory; Paste the RainbowGUI.jar in there.
Launch your Labymod client.

If you have any problems with the addon/have update ideas, feel free to

Open an Issue here or
Open a ticket on my Discord Server in this channel