When sodium is dissolved in liquid ammonia, a solution of deep blue colour is obtained. The colour of the solution is due to

Solution :
The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus imparts blue colour to the solution.
$$M + \left( {x + y} \right)N{H_3} \to $$     $${\left[ {M{{\left( {N{H_3}} \right)}_x}} \right]^ + } + {\left[ {e{{\left( {N{H_3}} \right)}_y}} \right]^ - }$$