Galactic Night is an experimental nightmode app for rooted Samsung Galaxy S2, S3 and Note 1 phones (don't bother trying on other devices) that lets you set various color modes on your phone for use in the dark, to save batteries, for astronomy, ebook reading in the dark, and more. It's designed to work on Android devices that have root access, and it requires a rooted device to work.

There are a lot of color modes that can be used. It can be used for reading books and e-books. It can be used for saving battery power. It can be used for reading and viewing images.