How can I change the design theme?
Threema is available in a light and a dark theme. You can switch between the two themes here:
Settings > Appearance > Design theme
Settings > Chat Display > Dark Theme
Threema respects Windows Phone’s system-wide color-scheme setting, which can be adjusted here:
Windows Phone > Settings > Start + Theme > Background
Colored chat bubbles can be toggled in Settings > Appearance > Colored Chat Bubbles.