The National Museum of CW Medicine shows the flag at:
http://www.civilwarmed.org/shop/product.htm?id=1732
I would believe it to be the solid red flag.
George Martin
Note also:
http://alexandersbattalionfieldhospital.com/about.htm
PLEDGE TO THE CONFEDERATE HOSPITAL FLAG
I PLEDGE TO ALWAYS HONOR THE CONFEDERATE HOSPITAL FLAG AND THE MEMORY OF THE SURGEONS OF THE WAR WHO SERVED UNDER ITS CRIMSON RED; RED FOR MEMORY OF THOSE WHO SUFFERED AND DIED WHILE SPILLING THEIR BLOOD FOR THE CAUSE, RED FOR THE SURGEONS WHO WORE THE BLOODSTAINED APRON, AND RED FOR THE EYES THAT CRIED FOR THE MEMORY OF IT ALL.
AUTHOR UNKNOWN CIRCA 1902--WRITTEN DURING A VETERANS REUNION BY SURGEONS ATTENDING