i used to buy chicken and there were lotsa black bones, lott of broken ones also. everything mechanical in processing. the black tho mebe from injurys sustained earlier on. possibly from blood internal hemorage??? not uncommon in assembly line birds.
Personally, if it were me, I would take it back to where you bought it and get a new/fresh bird. It's just a chicken so either way, I can't see the store not taking it back in exchange.
If they don't, pitch it and get a freash bird for $5-6 and be confident you're smoking and eating a healthy bird. Getting food poisioning, etc. in order to save a few bucks will cost you more in the long run.
The bones turn black because it was frozen. Chickens which were never frozen , the bones aren't black, if they are than you know it's been frozen , then thawed to try to pass it off as fresh never frozen.