I found this among some old Lefty Frizzell recordings.

BALLAD OF THE BLUE AND GREY
As recorded by: Lefty Frizzell

Now Jimmy chose the Yankee blue
His heart was on their side
But brother Billy joined the rebs
And how their mother cried

They both shook hands and kissed their mom
There wasn't much to say
One headed north the other south
The blue against the grey

It was brother fightin' brother
Father fightin' son
A war that both sides had to lose
No matter which side won

Bill was in the charge at Gettysburg
He'd never known defeat
While Jim was up there on the hill
He prayed they'd never meet

With Jim a dozen yards ahead
The Yanks came down the hill
And when the smoke had cleared away
Jim found his brother Bill

Jim knelt beside young Billy
But he had no words to say
For Bill saw him and held his fire
While Jim had blazed away

It was brother fightin' brother
Father fightin' son
A war that both sides had to lose
No matter which side won