Thread rename - done
Setting the the Colour mode to Light or Dark is useful when assessing Colour palettes and Icon themes, but to set it back to System default the user will have to :
And if they forget, when they change the mode in their OS settings they'll be asking here -
"Why is calibre ignoring the Color mode I have in my Linux/MacOS/Windows system settings?"
Added: why not toggle around the three permissible values, if not that… what?
BR