iOS 8 includes a new greyscale mode that could benefit people with visual impairments. The new mode is included in addition to inverse color which was previously available. The new option will reduce the bright colors and possibly reduce glare to make the screen easier to see. Greyscale and inverse color can be enabled simultaneously for further visual changes. Even for people without visual impairments greyscale maybe made the screen slightly easier to view outdoors.
To enable greyscale navigate to Settings > General > Accessibility > Greyscale. Please note that the above screenshot is an altered colored screenshot.