Apple iPod nano (7th generation) - Manual (Page 50)

Chapter 11 Accessibility 50
Quickly activating accessibility features
You can set iPod nano to switch Invert Colors or VoiceOver off and on when you press the Home
button three times. This makes it easier to share iPod nano with another person who doesn’t
need the same features.
Turn on the accessibility shortcut:
1 On the Home screen, tap Settings > General.
2 Tap Accessibility.
3 Tap Triple-click Home, then tap one of the options.