Although a well known subject over many years,always in every publication with the red Höllehund untill recently on this blogspot
http://theprofilepaintshop.blogspot.se/
It "is" black and outlined in red,looking at the photo I included he is probably right.
An old article in SAM of Sept.1979 on this,describes in brief an eyewitness account of a W.S.Walton of Ham Surrey who performed some measuring and colour matching at the time,I wonder how he saw it,anyone has a copy of his notes?