Implemented using a ColorModeMenu class,
derived from ToggleActionMenu (derived from KActionMenu),
as a child object of PageView.
* KToggleAction for every color mode, allows to set shortcuts for every mode.
Color mode actions have icons.
* KToggleAction for normal colors mode.
* ToggleActionMenu containing all color mode actions.
If triggered, toggles color mode between normal colors and last change colors mode.
"Toggle Change Colors" is replaced by "Change Colors", which is actually a toggle action.
BUG: 407217
BUG: 437755