[ZOLTAN190D]

Yes, indeed it was only a speculation.I am not a Ju-88 expert but it was common in the Late Luftwaffe such rebuildings(see FW190 A into FW-190D).On the other hand, I was at the beginning suspicious about the accuracy of description, but after I read all the descriptions of the planes downed over England, this a/c was the only one with this unusual color.All the other colors were the standard RLM Farben used then, well described in reports.
However, two things caught my attention: the greenish-blue(so-called many years ago RLM 84, similar to the British duck egg blue)was present on German bombers and intruders early 1944, maybe late '43.
But as a He-219 expert, for me, a revelation was that all the bombers and night intruders over England late 1943 early-mid 1944 described at this site were painted in black, underside.
Almost certainly this indicates that this color was used only over the territories dominated by RAF to camouflage Luftwaffe intruders into RAF night fighters.
Applied this to He-219, R.Francis Fergusson's (I am very impressed with his work-The best book about He-219) theory- about that this color was applied over a certain A-2 290 Wk.Nr. batch - fail.