Fixing a Container GUI That Still Looks Vanilla After Installing Recolourful Containers
You installed the pack, but your chest or furnace still opens with the same old grey interface. This is almost always a load-order or conflict problem rather than a broken pack.
Rule out load order first
Go to Options, then Resource Packs. In the Selected column, Recolourful Containers GUI + HUD must be present and positioned above any other pack that also edits GUI textures. Resource packs apply top-down, so a pack above it that includes container textures will hide the recolored versions. Drag Recolourful Containers to the top of the Selected list and re-open a container to test.
Rule out modded or replaced GUIs
If only some containers look wrong, note which ones. Screens added by other mods often ship their own GUI textures and will not be recolored by this pack. Likewise, if another mod rewrites the vanilla container screens entirely, its textures take priority. Test in a fresh world with only this pack enabled to see the intended look, then re-add packs and mods one at a time until the screen reverts, which tells you exactly what is overriding it.
Refresh the view
After changing resource pack order, close and reopen the container, and if it still looks stale, leave and re-enter the world so the client reloads textures cleanly.