There is only Light and Dark theme and Same as system. I have sent a screenshot named “color theme”, so “Color theme” option in OO mobile app settings.
Add these two suggestions or just custom color theme(option b.):
a. Add more colors so that we can choose like dark grey, dark blue, grey, brown, red, blue, purple etc.
b. Add an option for custom color themes. So to choose any custom color theme we want.
If You don’t want to add option a. then at least add option b.