I have seen them black…I have seen them light grey with yellow stripes…and I have seen them in a duck-egg blue sort of color with yellow stripes… I think I have some pics of the Fritz at home…I’ll have to look.
Until I find it-- this site has some pics…Fritz is near top left of the list under AP bombs…they are mainly drawings…
most of my research found that they are RLM 66 Dunkel Greu, not black as I thought for the longest time too but when I was at the Imperial War Museum at Duxford England I asked one of their restoration crew members and they showed an UXO from WWII London during the Blitz that was not touched since then and it was a very dk grey even Testors MM Engine Grey looks very close to the color