In a hardness test on feedwater, what color indicates the presence of hardness?

In hardness testing of feedwater, the color red is significant as it indicates the presence of hardness. This method typically involves using a reagent that changes color in response to the hardness ions present in the water, specifically calcium and magnesium. The appearance of red signifies that these ions have reacted with the indicator used in the test, confirming that hardness is present in the water sample being tested. This is an essential part of maintaining water quality, as high levels of hardness can lead to scale formation and other issues in water systems. Understanding color changes in these tests is vital for interpreting results accurately in water quality assessments.