As others have pointed out, it is a dye used in poisons to show it is there. To quote George Carlin "I am always thinking big questions like, Why is there no b

As others have pointed out, it is a dye used in poisons to show it is there. To quote George Carlin "I am always thinking big questions like, Why is there no blue food?". This is also why most food handling gear in manufacturing is blue coloured. Easy to see. Vaguely related,there was a small chemical spill near my house about a month back and it made it to the local creek. You could tell because they add that neon blue dye so that it is obvious when there is a spill. https://www.theguardian.com/environment/2025/jul/17/banyule-creek-melbourne-rosanna-blue-discoloration-chemicals-epa-ntwnfb https://www.theguardian.com/environment/2025/jul/17/banyule-...