One major theme that plays through out Cormac McCarthy's novel "the road" is death.
The man and the boy  struggle to survive, death is the obvious theme because there is a constant threat of murder and running out of food . The landscape is covered in ash and soot . Most living things were killed . Civilization has been completely destroyed by the big mysterious event . For example, cows are extinct, and the boy has never before seen birds or fish. "On the hillsides old crops dead and flattened. The barren ridgeline trees raw and black in the rain". 

Eventually  the reader become aware that the man is dying. "In the night he woke in the cold dark coughing and he coughed till his chest was raw.... He knelt there wheezing softly, his hands on his knees. I am going to die, he said. Tell me how I am to do that" . His death is approaching , his worsening cough and the increasing amounts of blood he spits out, are evidence of that .

The color of the scenery and landscape thoroughly represents death. the overall tone is black and grey . the ash ,the water, the rain , the burnt trees. Bleak landscape  in general gives and ambience of death and depression. The interesting about this book is that death is expected and even accepted by the characters. When the man shot a bandit that was trying to get the boy. he didn't  give a seconded thought about shooting him. He just accepted the bandits death and didn't think twice about it.