For the first time I saw this plant as someone was selling it in a dry form with a statement “keep this in water & it will turn to green completely”. Initially I thought it as a prank but later on decided to purchase it.
I asked some plant expert & also did a research from my end.
What he said was exactly the same happened . This plant name is selaginella and also known as Sanjivani.
Under dry conditions, some species of this can survive dehydration. In this state, they may roll up into brown balls and be uprooted, but can rehydrate under moist conditions, become green again and resume growth.