Board Thread:Questions and Answers/@comment-116.65.70.72-20130727121600/@comment-5527544-20140113124751

When their color timers are flashing (those with the time limit), it means the Ultra is running out of energy, they can no longer fight, they have three options, risk death by refusing to change back, immediately change back to human form or get an energy boost/recharge from somewhere.

If it goes out it means exhaustion and you can die from exhaustion. It means they are in a state were they life if fading and they are too weak/tired to move.