Michael,
of course you meant D.VII F 4253/18, I know. As this is one of the most discussed aircrafts of World War 1. The controversial about the possible black or red nose is fulfilling almost all forums addicted to this subject. There is no evidence about the one or another. So sadly I think you will remain in uncertainty
Udet himself wrote in his book only about "a red plane" without further details. As a Jasta-Leader at this time he had maybe 2 coincident aircrafts in service? Another aspect is, that Goering took over and flying the 4253/18 after Udet was wounded. And again here comes another irritation weather it was painted white all over or white with a red! nose. As commader of Jasta 11 he might have had also two similar planes when he flew 278/18, 294/18, 4253/18 and 5125/18
Confused
Thomas