In general, Mystery Tie Dyes will develop green. Mine has three small green spots. I got mine indirecly from kmaintl. I do not know exactly how old it was when I purchased it from the fellow who bought it from kmaintl, but it was about the size of a quarter or half dollar when fully inflated. It had very very tiny trace amounts of red. The green took about 6 months to develop. I've now had it for almost a year. Still no purple. I paid $225.
Now, I've seen people call this mushroom a Jawbreaker, and you can refer to kmaintl's response above to clarify that. But, I know that locally, there are at least two other strains of "Jawbreaker," mushrooms that DO NOT get green. I have never heard anyone refer to these two strains as Mystery Tie Dyes. So, if you want a better guarantee that you'll get the green and possibly purple, then I suggest you seek out a Mystery Tie Dye. Or, better yet, just make sure the person you're purchasing from can provide you with a photograph of the mother mushroom, and make sure that the mother shroom has the colors you desire.
As far as hardiness, I can't say that I've knowingly done anything to stress it, so I can't really comment there. I try to keep all of my coral healthy and stress free.
I hope that helps!