Christian,
Thanks much for your observation - they're most helpful.
I'd like to show 3 pics from the Derfflinger video on YouTube - it's essentially a photo album so print screen was easy. I can't testify for the authorship, but it strikes me as a kind of labor of love. I know from past experience that the WWI German Navy has some very dedicated students. (They claim Derfflinger was called "Iron Dog" but its crew - never heard that one.)
Below is a sobering pic of DF's bad damaged turret which, as I recall, took some very good damage control when hit to prevent even more serious damage. There's nothing on top, but it's possible that the paint was either burned off or scraped off:

The next photo shows more repairs to the superstructure and guns. It does appear that the turret has been painted on top although it's hard to see black there - perhaps old black and white photo could distort that. What is not possible to see is a circle and I doubt that would disappear.

The last photo shows DF immediately after repairs are finished. You can see the change in mast camo that Tanner mentioned. The top of the turrets are clearly very dark - but if there are circles there I don't see them. And this photo is very rare to my eyes. Most pics of German BBs that show the circles etc are taken from the air - illustrating why they were of value. This one is taken from the surface but at an angle that allows a good look at the front turrets.
(I still don't see fear of air attack coexisting with circles on the ship. Stupidity exists in war of course. Many German tanks in Poland had large white national markings which were immediately removed when they found that Polish gunners were using them as a target. The Japanese quit putting large hinomarus on ship decks after Midway, guessing correcting that US dive bombers were assisted by big red "bulls eyes" on their target.)

Many of repair photos suggest that some serious weathering would be in order for the hull. A couple of years back I did the ICM Konig and remember mulling this over. The German fleet was well exercised, but spent much time in harbor. But I'm not sure that sitting in salt water would look pristine unless there was an ample supply of paint available and the will to use it. Tanner mentions that when the Brits examined the ship on arrival in Scapa Flow that they found the paint bunkers empty. What we'd need is a lot more high quality photos of German ships at sea and sadly I doubt we're going to add greatly to the limited supply available which are pretty ambiguous.
A factoid: the Brits raised Derfflinger at Scapa Flow - but didn't finish scrapping the vessel until 1948: three photos on that matter in the video. Reminds me of the day in the early 70s when I had a close up view of the scrapping of an Essex class carrier which had been mothballed in the Sacramento Delta. A worker thought it was Essex herself. A sad sight really.
Eric