There is no white colour. The bottom part of the front engine cowling was painted with the RLM76. Possible the part could be damaged and being repaired , was painted with the light colour a little bit higher than the entire rest of the cowling. Also the part could be taken from an another plane with the higher demarcation line for the camo colours. But I think the first reason is the most likely. Additionally the smudges and lighter spots are the result of wipping or washing the areas with a rag and the paint peeling off.
Was there an Ar 234 C-3, WIN 250125, 20/EJ6 2, Bertin-Tempelino, Germany, autumn 1945? And do you have a photograph of him? As far as I know, he was the carrier of the Mini Arado.
I found this image where the stroke color is different from the number. Is it possible that one or both engines were replaced on this aircraft in the same way as on the Ar-234 F1+AA?