I can tell you for sure that copper sulfate will be added to the swimming pool to kill algae and other plants, but the blue color of swimming pool water is definitely not caused by copper sulfate! The maximum amount of copper sulfate added by the state is per liter 1 mg, so it is impossible for such a small dose of copper sulfate to turn the pool water blue.

The real reason lies in the refraction of the sun's light, just like all the sea and the sky you see are blue. It is impossible for someone to add copper sulfate to the sea ... Generally speaking, the deeper the water in the pool, the bluer the water will be. This is because water absorbs more red, orange and yellow in sunlight and reflects more blue and purple, so we will see blue.

By the way, I forgot to say one thing. I think your question is like a chemistry topic. If yes, you can answer according to copper sulfate. This is a typical topic produced by China, which is seriously inconsistent with the objective facts. It's all about the topic, and I don't know how many teenagers I hurt. ...............................