根據復分解反應發生的條件可以得知，藍色的硫酸銅溶液與氫氧化鈉 溶液 反應生成硫酸鈉和 氫氧化銅 沉淀，由于該反應是在溶液中進行的，所以生成的是無色的 硫酸鈉 溶液和藍色的氫氧化銅沉淀，故反應現象應當描述為:溶液變為無色，并有藍色沉淀生成.

According to the conditions under which the double decomposition reaction takes place, the blue copper sulfate solution reacts with sodium hydroxide solution to form sodium sulfate and copper hydroxide precipitation. Since the reaction is carried out in the solution, the colorless sodium sulfate solution and the blue copper hydroxide precipitation are formed, so the reaction phenomenon should be described as: The liquid becomes colorless with blue precipitation.