Supernatural makes vigorous use of visual imagery to support the narrative.  Just one more example: color.

The association of the color white and death started with the two Women in White early in the first season

From there, Dean and John stripped down to their most vulnerable, with little left to hold them here.

Hints of death showed up in What Is and What Should Never Be.  The girl, John, and Mary weren’t really there.  It was all a dream of those long gone.

It was a dream where Mary was associated with pink and red flowers and Sam with yellow flowers.  It was Dean, on the brink of death, who was associated with white flowers.

Sam wore the blue and white shirt of sacrifice and death at the end of Season 2.

White has hinted at death throughout the remaining seasons.

Until here, in bold, Death rides the palest horse.