Historical Rules · 1 June 2020
Rule 611.3b
Official source text from the 1 June 2020 Rules release
The effect applies at all times that the permanent generating it is on the battlefield or the object generating it is in the appropriate zone. Example: A permanent with the static ability “All white creatures get +1/+1” generates an effect that continuously gives +1/+1 to each white creature on the battlefield. If a creature becomes white, it gets this bonus; a creature that stops being white loses it.