Sometimes its a HIT and MISS situtation.....
right now i have 4 IT (2 7.5", 2 5.5") 2 of them 1 7.5" and 1 5.5" are always stable no matter what happend. ei: waterchange, feeding, bullying around, open light etc. but the other 2 ITs their stableness are on and OFF....
so if you will buy an IT look for an IT with a stable color.... chances are when you put it in your tank it will be stable.... though likewise its a HIT and MISS situation cause sometimes in your tank they are always unstable once you sell it and placed to a new tank it becomes 24/7.... hehehehe and that sucks if ever...