I dont think it is black that has faded as red is the colour that fades the fastest under UV. So the red would be very pink if the black had gone blue.
It was news to me to and I ended up repainting a quarter scale gee bee and i know have shares in tamiya due to the amount of tape involved.
It makes sense really they are red white and blue rather than red, black and white as i guess far more patriotic etc. There used to be a video on youtube from one of the Delmar GEE BEE R repro documentaries where a GEE BEE expert talks about the colour schemes and that made me change mine. I googled it but could not find it, so someone with better googlefu than I might be able to help.
Anyway most importantly the model looks great and cant wait to see the end result