"Six white horses in a line
Six white horses in a line
Six white horses in a a line
Going to carry me to my burying ground"

Blind Lemon sang about being carried to his grave in a hearse pulled by six white horses, and I don't think he was wealthy.

"Six white horses and a rubber-tired hack
Gonna carry me to the graveyard and they won't bring me back"

Without thinking a whole lot about it, it seems like six white horses is a fairly commonly used image. And as an image, it sure is more visual than six black horses, or six variegated color horses.

Jerry