Yellow, Orange or Reddish Brown Water
This problem is sometimes seen first thing in the morning, or after periods of lower water use. It is also seen at seldom-used faucets. The water should clear after flushing the faucet briefly. The cause is most likely galvanized iron plumbing in the building. It does not indicate that the plumbing is about to fail or that it needs to be replaced, unless there is also a noticeable reduction in water pressure.
If this is only occurring with hot water, flushing the hot water tank may help by clearing out the sediment in the bottom of the tank. Hot water increases the rate of corrosion in plumbing. You may want to consult a plumber for safety precautions.
If the discoloration is sudden, there may be some activity that has disturbed the direction or rate of flow in the water main, such as use of a fire hydrant or a water main valve in your vicinity. This should clear on its own. Try running the water for a few minutes to see if it is clearing or still discolored. If the water does not clear, let the water sit for an hour. Then run the water for a few minutes and flush the toilet a couple of times.
Brown or Black Muddy Water