Why not go with the vinegar? I have never used retayne. Mother always used the vinegar rinse if something was fading.
She would wash it first, and if it faded, she would pour in some apple vinegar and if the first rinse did not do it, she used a
second rinse. Then rinse the vinegar out. I aired it outside on the line if the vinegar smell was in it a little. Why buy retayne when vinegar will do nicely. I am sure it is much cheaper.