Minecraft wiki entry for Development_versions, associated text: Potions that have missing or invalid potion-effect tags now default to the uncraftable potion, which now has no glint, and is now magenta in color.
This also applies to lingering potions, splash potions and tipped arrows.
Due to the water bottle without tags being changed to uncraftable potion, the brewing icon is also changed to uncraftable potion in the creative inventory.