Forum Flora Germanica

Or is it red, it strikes me as pink.
http://agrozoo.net/jsp/Galery_one_image ... 48d6acd1a8
The only fruit infected, all around the fruit. No idea why others not, it was in pile of fruits.
I think I have once probably seen same thing on old buried bones.

Any idea ?

Not really ...
One example for a red/ pink fungus is Hypomyces rosellus, but later on this develops those little round structures, and it is not growing on fruits, mainly on wood and/or old fungi.

The bacteria Serratia marcescens may grow on humid material, especially if this contains starch (on bread, on mushrooms, but even in bathrooms ...)

Several "moulds" (in a broad sense) can develop red to pinkish colours.
https://www.haus.de/leben/roter-schimmel-30391 (I linked this site only because they mention different species, as Neurospora crassa, Aspergillus versicolor, Fusarium oxysporum and Fusarium proliferatum).

Without microscopic details there will be no satisfying result.

This is kind of woody as it is shell of not decayed juglans fruit shell, from last year, and it is pretty dry. Besides of aerial moisture < bathroom there is no extra moisture.

About bones mentioned in OP, once I was in local church, man told they dug out bones from church wall and they were pink. Story tells that they painted nobility bones pink and walled it. The ones I dug up were from animal, buried like 15 cm in ground in sandy soil, colored as OP juglans fruit.

No luck googling around that, if anyone interested and google lucky ...