While I was looking for a roofed forest with dark oak trees, I noticed at night that the creepers when they are ready to blow, they flash from its normal color of green to completely white. This bug is in both creative and survival. I've noticed this in snapshots 14w08a through14w11b.

1. Wait till night.
2. Find a creeper.
3. Get close enough to creeper till you hear hiss or ignite it with flint and steel.
4 Watch it flash before it blows up.