After a generator is repaired, The Entity blocked the generator with the most progress for 30 seconds.  You see its white aura during this time.

Performing the Damage Generator Action on a Generator applies Overcharge:

The next Survivor interacting with that Generator is faced with a difficult Skill Check.
Failing the Skill Check results in an immediate Progression loss of 3/4/5 percent.
Succeeding the Skill Check grants no bonus Progression, but prevents the Generator from exploding.
After Overcharge is applied to a Generator, the following effect applies:

Increases the Regression speed from 75 percent to 200 percent over the next 30 seconds.

After picking up a Survivor, all Generators not currently being repaired by Survivors are blocked by The Entity for the next 16 seconds.

The Auras of blocked Generators are highlighted to you in white.
Thrilling Tremors has a cool-down of 100/80/60 seconds.

The Auras of Survivors, who are healing or being healed, are revealed to you when they are within a range of 20/24/28 meters.