what does it mean if your water is brown
The third likely source of brown water is iron (and/or manganese) in the water. As rain falls or snow melts on the land surface, and water seeps through iron-bearing soil and rock, iron can be dissolved into the water. In some cases, iron can also result from corrosion of iron or steel well casing or water pipes.
After determining that the brown water is coming from the cold water tap also, it is still possible that there is rust in the plumbing fixtures or the piping, but it would typically manifest in only one sink or tub and not uniformly throughout the house (unless the rust is in the main water pipe from the well).
If all on same water heater and both hot and cold are brown, or only one or the other is brown in the bathroom, might be a pipe with heavy rusting or iron bacteria buildup or sediment got knocked and loosened up a bunch of buildup, in which case flushing it out would clean it up (till the next time).