Rainbow Colors
The breed of pigeon that this is may not be known to us, but it certainly is a beautiful bird. While it was searching for food, there is a remote possibility that it ended up in the bucket of dye that someone else was using. That would explain why it is colored like a rainbow.
Considering that it is dangling near the window of somebody, it is possible that it is there to convey a message. After all, information could be transmitted over great distances in the past by using pigeons and owls as carriers. It’s also possible that the bird is a snitch sent to check up on someone; you just never know.