If you leave the spuds in a dark cupboard that the green tinge goes away and they are OK to eat again. They only go green when exposed to light.

yes, unwashed spuds do keep longer, but washing them removes any soil nematodes (small worm like parasite) that can cause rot. This isn't a concern for people, but it can be detrimental to potato production and potatoes found to be infected are unsaleable. They are also an export conern, so I would assume that maybe washed potatoes have been imported?