Why do we store silver chloride in dark coloured bottles?
Silver chloride gets decomposed by sunlight. Sunlight contains photons- a source of energy which decomposes silver chloride to silver and chlorine.
2AgCl(s) → 2Ag(s) + Cl2 (g)
So to protect from the decomposition of silver chloride by sunlight, they are stored in dark coloured bottles.
As the chemical reaction occurs in the presence of sunlight, so the reaction is known as photochemical reactions. It is an example of the photochemical decomposition reaction.