Use the Accessibility Shortcut. Press the Home button quickly three times to turn any of these features on or off:
VoiceOver
Zoom
Invert Colors
Hearing Aid Control (if you have paired hearing aids)
Guided Access (The shortcut starts Guided Access if it’s already turned on. See Guided Access.)
Switch Control
AssistiveTouch
Choose the features you want to control. Go to Settings > General > Accessibility > Accessibility Shortcut and select the accessibility features you use.
Not so fast. To slow down the triple-click speed, go to Settings > General > Accessibility > Home-click Speed.