Is the red spot floating above the water? If it is, I'd say the floating came first and the redness second.
Is the fish a Fighter?....does it have the will to live!? If it still tries to act normally, (eating food, swimming to see you) I would not give up on it just yet.
The floating means too much gas inside the fish, this sometimes can be digestive/food issue or a float bladder issue. Does the fish eat?? (Do not feed it peas, they cause gas) There may be food that could help with the digestive part. The swim bladder would take some anatomy knowledge and medical supplies to attempt treating.
The fish also won't recover if it is upside down, sounds silly, but weigh the fish down so it floats the right way and stays underwater. Fish are often tagged on their fins by conservation, I figure an earring through the lower fins would be a reasonable way to weigh it down. (wrapping cords or bands around the fish is a worse idea IMO)
Just some options, food for thought. Don't be discouraged by whatever may happen to the fish or the choices you make