Is it normal to have slight bleeding after wisdom tooth removal with bone graft after 3 days ? particularly after eating and/or doing saltwater rinses ? thanks?

Yes you have an open would filled with a blood clot and granulated bone and probably covered with a membrane to hold everything in pace during healing. any food that pushes on the would may squeese out some blood from the clot that would stain the saliva red. Keep upthe salt water rinses and continue with a soft diet on the opposite side until you return for your post Operative appointment.