The yellow might be from rust. Some of the older mains are made of iron. Most of the time, they are replaced by plastic ones. Another possibility is mud.
The smell could be any one of a number of things. For example, a muddy smell is usually from geosmin, produced by algae/bacteria (depending on how you classify them). You can also get a moldy smell, a sulfurous smell, or a few others. I suggest that you don't rely on Y!A but call your water supplier and tell them exactly what the water looks and smells like. They might ask you to take a sample of the first water to come out in the morning, even before you wash, brush, or flush the toilet. If you are having a problem, other people may be having the same one and the supplier will want to take care of it. Just hope that the problem is not something between your house and the main. That could be expensive.