Six horses (all of the same color) are traditionally used in a military funeral. White horses are used for someone of note - I know Jefferson Davis, Abe Lincoln, and Kennedy all had Six White Horses.
That term is used in many songs including the one you mentioned, a Greadful Dead song, and it makes me wonder about the children's song She'll be coming around the mountain (driving six white horses) when she comes.
It may have originated from the Bible - here's a passage I found.
BEHOLD, THE LORD COMETH WITH TEN THOUSANDS OF HIS SAINTS, TO EXECUTE JUDGMENT UPON ALL, AND TO CONVINCE ALL THAT ARE UNGODLY AMONG THEM OF ALL THEIR UNGODLY DEEDS WHICH THEY HAVE UNGODLY COMMITTED, AND OF ALL THEIR HARD SPEECHES WHICH UNGODLY SINNERS HAVE SPOKEN AGAINST HIM-Jude 14,15.
AND I SAW HEAVEN OPENED, AND BEHOLD A WHITE HORSE; AND HE THAT SAT UPON HIM WAS CALLED FAITHFUL AND TRUE, AND IN RIGHTEOUSNESS HE DOTH JUDGE AND MAKE WAR. HIS EYES WERE AS A FLAME OF FIRE…AND HIS NAME IS CALLED THE WORD OF GOD. AND THE ARMIES WHICH WERE IN HEAVEN FOLLOWED HIM UPON WHITE HORSES, CLOTHED IN FINE LINEN, WHITE AND CLEAN...HE HATH ON HIS VESTURE AND ON HIS THIGH A NAME WRITTEN, KING OF KINGS, AND LORD OF LORDS-Rev 19:11-14,16.
[ September 13, 2003, 06:32 AM: Message edited by: Connie ]