I've made it my personal mission to get to the bottom of this now, one way or another!!
Very curious... just did a picture search on google, for "black" "spoke nipples" & one of the first pics I got was the one I posted above. Same part numbers, everything, quoted on below KTM web site;
http://www.ktmcycles.com/catalog/PowerParts/wheels.htm
HOWEVER, in their desciption they refer to these as "anodised". Anodising is normally only used on Aluminium (although is used very rarely on titanium, zinc or magnesium (
http://en.wikipedia.org/wiki/Anodizing )).
I've tested these nipples with a magnet, and these are magnetic (ferrous alloy - i.e. carbon steel or ferritic/martensitic stainless).
Aluminium is non magnetic, so these cannot be aluminium. Additionally, these weigh more like c/s as opposed to aluminium for the same size component.
So as a minimum, the product descriptions on the KTM web site are incorrect.
I'll get onto KTM & see if they can finally clear this up, although this further supports the black oxide theory suggested by Dr Freaky...
I'll carry on the happy hunt!
Crispin