I've never heard of boiling an egg for 2 days. I'll have to ask some Jewish friends about that. Sounds kinda yucky ... but what do I know!
I do know that tea-eggs are twice boiled - once until hard and then again in dark tea until they absorb the flavor and color of the tea. You get the same grayish green ring around the yolks in those eggs, too, but they're yummy.