Create a higher contrast theme
Either be able to adjust existing colors,(darkening, or lightening) or choose from a simple palette of colors, or provide a variety of established themes. Providing the entire theme is hard to fit each user's preference. Allowing a few options with customization capability would be best.
4
votes

We added a dark theme, see this post for details:
http://blog.getitdoneapp.com/2016/06/manage-it-may-news/
This update sets us up to add more themes in the future fairly quickly.