The July Sky and Telescope has a great article on a "Red Light Field Test". The test showed that orange works better for preserving night vision than red. A nice feature might be to select color for night mode. Two approaches:
Option 1. Simple setup selection between red and orange
Option 2. Default red. But a box to select color from a color palette.
iOS accessibility features enable you to triple-click the home button to go into a color mode. The color can be selected from a color palette. This is important even if you use the SkySafari Night Mode because SS can time out, and when you open your iPhone/iPad, the Home Screen will spoil your night vision if your phone/tablet isn't in color mode. For those who don't know how to do this, please see this article to explain how to set the color, and how to set up a triple-click shortcut to toggle this mode: