Is the blank sample of hash ammonia nitrogen reagent green and normal? Why?

This is not normal. This reaction produces indigo dye. Hash ammonia-nitrogen reagent is a chemical reagent used to detect ammonia-nitrogen content in water. When in use, ammonia nitrogen in water can be converted into nitrate, and the ammonia nitrogen content in water can be indirectly determined by measuring the concentration of nitrate produced, but the indigo dye produced is indigo blue in color, not white-green, so it is abnormal.