Thank you for your answer!
One of the fishes has more than a half of the body black (we can say, it is black), the others are grey-yellow and grey-red. One of the grey-red, a female, is injured. She’s feeling better now, after the first dinner in my house.
Tomorrow I’m busy all the day, but after tomorrow I can return the extra fishes back to the pet-store.
Thank you! God bless you