why do dry sodium chloride, the solutions of sodium nitrate and solution chloride all impart the same color to the flame?

Answer 1

The flame color is due to the excitation of the Na^+ in the flame. Solutions dry out in the flame so there is no difference between the solid and the liquid. The yellow color you see is due to the Na and not nitraate or chloride ion

Answer 2

Thanks a lot for this solution.