Silver chloride is stored in dark coloured bottles so that not to expose to sunlight as when exposed to sunlight it decomposes to form silver and chlorine gas (hint: dark and white photography , photolysis ) I hope it will help you ??
Becoz it is an photo decomposition reactant and 2AgCl—->2Ag+Cl2
Silver salts are photosensitive compounds. So, when kept exposed to sunlight, it decomposes to form Silver metal. So, they are usually stored in dark coloured bottles.
Because it reacts with sun light
Silver chloride AgCl is sensitive to sunlight.when exposed to it,a salt decomposes into silver and chlorine. In order to check the decomposition, silver chloride is kept in dark coloured bottles so that sunlight may not fall on it.