Buttons make common actions more obvious and help users more easily perform them. Buttons use labels and sometimes icons to communicate the action that will occur when the user touches them.
How the buttons are viewed with various colour blindnesses
How the buttons are viewed with total colour blindness.
How keyboard navigation works with buttons.
Primary button [button].
Secondary button [button].
Tertiary button [button].
How the buttons demo is described by assistive technology.
As read with macOS High Sierra VoiceOver.