Money or your life!

A man was walking through a deserted street. Suddenly a robber pounced on him and said his usual punch line " Money or your life!!!" . The man smiled and said "My brother, at this moment both have no value to me!". The robber was not ready to believe. He pointed his gun to the man's head. The man silently pulled a slip from his pocket and showed the robber. The robber silently left the place. The colour of the slip was pink!