Very Easy
1st Method
When user Clicks Btn 1 If CallTinyDbVal Nightmode=Night Then Append Data Tag Nightmode Val = Daymode. Store TinyDb Data as Tag Nightmode Val Night
Add This Step in EveryScreen
If CallValTinydb TagNight = Nightmode
Then Set All You Screen Visble Component Black and White
Else Set All Components Color To Normal
Second Mehoed
Use This Extension
If Nightmode on
Then Set all your Component Black and white
Else set to normal color