How to Invert the Colors on an iPad to White on Black
Without any additional apps, users with an iPad running iOS 7 or iOS 8 can invert the color scheme, turning regular black-on-white pages of text into a less eye-searing white-on-black. Rather than merely flip white and black, however, the option inverts every color. While potentially useful for working around color blindness, inverting colors also causes vibrantly colored apps to look bizarre and might make some pages harder to read. Enable the feature through the accessibility options on the tablet or in iTunes. If you find it too distracting, try an alternate solution to darken the display.
Invert iPad Colors
Apple includes the option to invert colors in the accessibility options. To reach them, open the Settings app and then tap "General" followed by "Accessibility." Turn on "Invert Colors" to apply the change. Inverting colors works across every app on the iPad, including those included with the system and those bought from the App Store. The flipped colors won't appear in the image if you take a screenshot, however. To reset the colors to their defaults, return to the accessibility options and switch "Invert Colors" off.
Create a Shortcut
"Invert Colors" flips colors universally without regard for an app's original color scheme. In a darkly colored app, the feature has the opposite effect, making the screen black on white. Rather than open the accessibility options over and over to enable and disable the feature, create a shortcut to toggle the inverted colors on and off. Scroll to the bottom of the accessibility options and tap "Accessibility Shortcut." Pick "Invert Colors" to set the shortcut, and thereafter, triple-press the "Home" button to change between regular and inverted colors without closing your current app. If you have trouble pressing the button fast enough, choose "Home-Click Speed" in the accessibility options and choose "Slow" or "Slowest."
As an alternative to the accessibility options on the iPad, set the option through iTunes on your computer. Connect the tablet, open its "Summary" tab in iTunes and click "Configure Accessibility" at the bottom of the page. Check "Invert Colors" and your iPad flips its color scheme immediately, without the need to sync. On versions prior to iTunes 12, the button is labeled "Configure Universal Access" and the option is described as "White on Black," but it applies the same feature as "Invert Colors."
Related Accessibility Features
Inverting colors is the most effective way to darken your iPad's screen, but because it causes other colors to look so odd, you might try a more moderate alternative. In the accessibility options on the tablet, press "Increase Contrast" to access toggles to "Darken Colors" or "Reduce White Point." Both of these options help to darken the screen without inverting colors. If you do invert colors, try enabling "Grayscale" on the main accessibility page to nullify the bizarre colors inversion causes.