Copper(II) nitrate and sodium sulfide

http://genchem.chem.wisc.edu/lab/CCA/MVHTM/CUSO/CUSONACO.HTM
a pale blue precipitate if formed.

-A pale blue precipitate is formed which is supposed to be insoluble copper carbonate. However, a flame test on the precipitate will be orange and I'm not sure why.

[I would assume why is because of excess sodium ions mixed in, sodium spectral lines and flame colors tend to overpower everything else.]