There is a good two volume set of books on German Naval Camouflage by Naval Institute Press which I refer to. The Agora Bismarck appears to capture the ship as she appeared on 21 May 1941 in Grimstad-fjord near Bergen. At that time, there were no black and white stripes on the superstructure and the tops of the four turrets were grey. The swastika and red surround on the fore and aft were obliterated by dark grey paint. This is not her final scheme as she was painted before leaving Norway for the North Atlantic.
The red band with swastika flags on the deck are synonymous with the black/white superstructure markings. So, to be accurate with that marking, the superstructure needs to have those markings applied too. What Ballard probably saw was the grey paint eroded away to reveal the earlier markings.
HTH
Mark Proulx
