Hi I'm Matt A male with breast cancer, I came across this site a couple of days ago, I've been reading a lot of blogs and has been very helpful wish I found this before I started my treatment :-), ...
Welcome Matt. Not sure about the purple toe part but a white nail means the nail bed is damaged and it might lift off. I stayed out of the sun with mine and while they all receded finger and toe nails alike I managed to keep them on until they grew out months later. Try to keep them trimmed so they don't catch on anything. Soaking the feet in water with epsoms salts may help.