When my house was built (about three years ago), the builders
neglected to paint the gas pipe on my side of my meter and that pipe
has now developed a nice coat of surface rust (it's normal black gas
pipe). The pipe on the gas company's side of the meter was painted and
looks the same as when I moved in.

When I put an addition on my house 15 years ago local code required wrapping
iron pipe in plastic to protect it.
It might be worth a call to your building department to see what they
required 3 years ago. There might be a big lawsuit brewing, if the
contractor is still in business.