Fingers going blue? It ain't necessarily the cold

My fingers had gone blue. It obviously wasn't the cold, so it must have been something I'd done.

Indeed it was. I hadn't looked closely enough at the Twisties packet I'd picked off the shelf at Spar.

There, in quite plain language, was: "turns your tongue blue."

That was a relief. Now I only had to answer the question regarding whether the the item should be listed under FOOD & DRINKS or under HEALTH.