From the menu select Settings --> Appearance --> Theme. Then click on the pencil icon. Then tap on brightness and make sure it is not 0%/100%. If it is 0% background will be black and white for 100%.
My app background is fully black/white.
From the menu select Settings --> Appearance --> Theme. Then click on the pencil icon. Then tap on brightness and make sure it is not 0%/100%. If it is 0% background will be black and white for 100%.