Redshift version >= 1.12 requires the -P option to clear the existing gamma ramps for one-shot mode. Without it the screen gets darker and darker until it is impossible to see anything.
Quoting from the redshift 1.12 manual page:
-O TEMP One-shot manual mode (set color temperature). Use this with the -P option to clear the existing gamma ramps before applying the new color temperature.
-P Reset existing gamma ramps before applying new color effect.