In the menu bar, there’s a simple Siri black and white icon that
features the word “Siri” surrounded by a box, while the full dock
icon is more colorful and features a colorful Siri waveform in the
style of other built-in app icons. Clicking on either of the icons
brings up a Siri waveform to give users a visual cue that the
virtual assistant is listening for commands, much like on iOS
devices when the Home button is held down.