Bonjour. In the US, there were Black Pilots during WW2. I am unaware of any US black pilots during WWI. Somewhere, I have read of a black pilot for the Russians during WWI, but unfortunately I do not have any references at hand. There was Eugene Bullard who joined the French Foreign Legion and later flew (see:
Eugene Jaques Bullard, which also has several references on Black American pilots).
As regards being buried in the same graveyards, I am certain no distinction as to race was made for UK and USA graveyards. Having seen many French and Belgian graveyards, I doubt there was any distinction, but I can't prove it-- I have seen many graves of Senegalese tireurs, etc., in French graveyards, alongside personnel from majority French units, so I do not think they were buried separately.
I think this subject has been discussed previously on this forum-- try the search function. Doc