Melissa, copper turns things blue so yes, I'd guess that is a normal natural reaction. Reading up on it copper sulfate is sometimes used to turn fireworks blue.
OHLD copper sulfate is a fungicide, algaecide, and herbicide. I knew copper was used in sprays for fruit trees and such but I didn't know what chemical form it took without research. In certain dosages it can be toxic to humans and I'd guess other animals and if you get it in your eyes you are in trouble. My guess is that Melissa is using it to treat the water to prevent algae growth. I could be wrong, it could be used to maybe stop the growth if mosquito wigglers. Or maybe something else. I haven't heard of using it for either and I don't know the correct dosage but it wouldn't surprise me if she read about it on this forum.
I handle algae growth by washing the water containers in a mild bleach solution when they start to turn green. I handle mosquito wigglers by totally dumping the water out of the waterers every couple of days before they have time to turn into mosquitoes. But my watering system is just bowls. If you have some type of automatic watering system such as nipples or some type of big vacuum tank where you store water for many days or weeks you may need to treat the water somehow to prevent algae, slime, or wigglers. I don't have any experience with those types of watering systems so I don't know how appropriate copper sulfate is or what the correct dosage might be. All I really know about it is that copper turns stuff blue.