For me it would depend on how much fabric I was washing. If it is a fat quarter, I would do it by hand in the sink. I would put my red FQ in the sink with very hot water and a bit of Retayne to set the colour. Swish it around with a wooden spoon for a while and then check the water and rinse. I would repeat washing until the water was clear. The white I would simply hand wash in the sink.
If it was yardage, I would do it in the washing machine with Retayne and colour catchers for the red.