The California Department of Water Resources and the city of Stockton are letting people know the water color change is on purpose and not to be alarmed. A dye, which according to scientists is harmless to people, boats and the environment, will be used to test the water as scientists examine harmful algal blooms at the lake. McLeod Lake’s water may turn pink or purple during the testing, according to the city of Stockton. The lake was selected by the state as one of the study sites because of the impact of those harmful algal blooms in the area, particularly during drought years.