Select one of the many colour schemes available for base16, look for the corresponding CSS file in the css folder and update your logseq/custom.css with the contents of the file.

Use a tool like Stylus.

Supported Features

Basic colour scheme
CodeMirror

To-do List

Graph colours
Left panel for small screens
A lot more that has been missed

Issues

At the moment I won't respond to issues, as LogSeq are still in the process of re-working their CSS to be variable based, so these themes have the potential to break at any release. As of 0.0.4, the prebuilt css files in the css folder work.