There is one type of algae called Oscillatoria rubescences that makes a very beautiful brownish color. Unfortunately, that algae also is a signal about poor a water quality. Even some bacteria can look pretty rusty. Thanks for the question. These are things like pipes from industry or other places that discharge fertilizer nutrients.
Lakes respond to fertilizer just like a lawn.
They get a lot greener. Sometimes, unfortunately, the source of nutrients may be diffuse and hard to stop. Some scientists have successfully used fish to make a lake less green. When a lake has lots of big fish, they eat the small fish, this lets the zooplankton grow, and the algae get eaten. This sounds pretty complicated, I know, but it's amazing that sometimes it works very well.