Press L on an object that gives off light (e.g., sconce, campfire, portal, mounted Dverger circlet) to set its color, brightness, and range. Also makes sign text glow with a colored halo, lit letters or an outline. Servers can limit it to admins.
Please note that the install buttons only work if you have compatible client software installed, such as the Thunderstore Mod Manager. Otherwise use the zip download links instead.