french bulldog has aggression towards certain dogs

Question
I have a 12 month old not neutered french bulldog. Who is very social and loves to play with other dogs. We have a neighbor cockapoo male who he used to play all the time, untill they got another cockapoo male who my fenchie wanted to eat for lunch the first day they brought him home. I thought that was because the little cockapoo wans neutered or because he was jelaous that he can loose his neighbor friend. Everytime we see them my dog has no interest with the older dog that he used to play. His eyes get bright red like a bull and he goes after the little 9mnth old cockapoo who was recently neutered.
He gets along preety well with other dogs when i take him to the  dog park. But few month ago  one dog attacked him who was black, so as the puppy that he doesnt like. Can he associate the color of the dog who attacked him by our neighbor's dog??
Thank You

Answer
Dogs don't see a whole lot of color, but surely can tell light and dark dogs apart.  After all, a black dog looks different in a black and white photo.  When it comes to why, we can only guess.  It could be more of subtle behaviors.  Things like body position, eye contact, ears, etc. can give a doggy '' Your mother wears combat boots'' message.  Even some neutered dogs will do it.  I once saw a neutered Husky challenge an intact Lab twice his size. Fortunately, both dogs were on leash.