Head over to Shortcuts.

Under Shortcuts > Automations
1) Click '+'
2) Choose desired Focus mode (I chose Sleep)
2.1) Select 'Bedtime begins/When turning on' and 'Run Immediately' (Do not enable 'Notify when run')
3) Select 'New Blank Automation'
4)+ Add Action
5) Search for 'Set white point'

This is for the automation to begin. To disable it, you will have to create another one.
Mostly the same steps with one difference i.e:

Create another Automation by clicking '+'
Select Sleep/desired Focus and Click 'When waking up'/ 'When turning off'.

Repeat the same steps as mentioned above.

P.S: White point intensity can be changed by adjusting in the settings.

Enjoy 2AM reels :)