You'll need a Mac and Xcode to install (but you don't need to be a developer).<p>Instructions video: <a href="https://www.youtube.com/watch?v=D_01P4-ubdA" rel="nofollow">https://www.youtube.com/watch?v=D_01P4-ubdA</a><p>If you get weird blue and yellow circles,<p>=> turn OFF <i>'Reduce White Point'</i> in <i>Settings / General / Accessibility / Increase Contrast</i><p>Note: it works because you don't need to be a developer to load apps to your iPhone via Xcode anymore<p>Note2: it uses "private" APIs so it won't be accepted into the App Store (just like <i>f.lux</i>).