What's in the water?

We drove from our spot in the Sierra Nevadas to Malaga to stay with a
friend, but we took all the back roads and saw maybe 3 or 4 lakes that
were all this vibrant terquoise color. Not sure what makes them this
color, maybe the same thing that makes the rocks and dirt so red... In
any case, they were really lovely so we stopped and dipped our toes in
a couple of times.