We went on vaca and shut off the water while gone for four days. Upon return, our hot water is brownish and the cold is fine and clear. What do I do?

Sounds like sediment in tank got stirred up. You could try drawing some water from the bottom of the tank to flush it as well as let the water run at a tap until it comes out clean.

The brown you see is Iron Oxide,( rust).
While PJ's advice about flushing your hot water heater was correct his description of how to do it wasn't. Here's how to flush a water heater,



For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule.

Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes.

Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back together the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. Hope this helps and thank you for rating my answer,
Tom