Use the "Blink" to make a property switch regularly between to states, without interpolation.

1. Select the property
2. Click on the "Blink" button

The Blink can be adjusted in the effects of the corresponding layer.

By default, with the "A/B Ratio" set to 50%, each state is set exactly the same time, changing this ratio can make the property stay longer on one or the other of the states.