Why sodium chloride on heating with sodium vapours acquires yellow colour?

Sodium propionate on heating with sodalime yields

Sodium acetate is heated with sodalime.

Sodium chloride present in ORS is -

Why does KCl turn violet on heating in the potassium vapours ?

Chlorine -water on standing loses its yellow colour - why ?

Why does table salt, some times appear yellow in colour?

In the electrolysis of aqueous sodium chloride solution, which of the half - cell reaction will occur at anode -