The melting point of any substance is its physical property.
colour of any substance is also its physical property.
However TNT is a chemical property. It is explosive as it dissociates into nitrogen gas , water, Carbon monoxide and carbon.
the reaction can be given as
2 C7H5N3O6 ---> 3 N2 + 5 H2O + 7 CO + 7 C
Due to carbon it gives as sooty flames