Why amonia solution of alkali metals are blue in clour?

Answer 1

Solvated electrons. The electrons "dissolve" from the metal. It's blue because electrons have a different absorption spectra.

Answer 2

The blue color of alkali metal solutions is due to the formation of solvated electrons. When alkali metals dissolve in ammonia, they lose an electron to form free electrons that react with the solvent (ammonia) to create a blue color. This phenomenon is known as the formation of solvated electrons and is responsible for the blue color of the solution.