I have some mushrooms that were blue when I originally bought them, after being in my first tank for a while they turned light purple. Then after being in my temporary tank for a few weeks they turned a velvety flourescent green.

Does anybody know why or how mushrooms accomplish this? I am not complaining about the color and I hope some of them retain the velvety green but this morning two of them were lavender/light purple again after moving them back to my main tank.