Good news for your eyes!
Backlog has released Dark Mode: 
There are now light and dark mode options for both web* and mobile apps. By default, Backlog is in light mode, but you can easily switch to dark mode from your Personal Settings page.
*Note: Dark mode appearance function is not available in IE 11.
How to enable Dark Mode:
- Go to Personal Settings, User Information tab
- In the Appearance section, select “Dark”
- Click “Submit” to apply the changes
And that’s it — dark mode in Backlog 
(For mobile versions, Backlog dark mode depends on your phone settings.)