I was giving today zinc -tablet to a patient directly to her stomach because she cannot move. The tube which I first used was not clean so it contained some medicine of the last use. The tube turned light blue like copper ion -blue after I inserted the zinc water to the tube. I have not managed to figure out what is the ion that causes the color. I will look at her medicine list tomorrow and get some extra pieces of information. Is there any Zinc -ion which color is blue?