To override this (or any other) theme in your personal config file, please follow the guide in the color theme documentation. This is handy for small tweaks to the theme without having to fork and maintain your own theme.
Clone and open this repository in VS Code
Press F5 to open a new window with your extension loaded
Press Cmd + Shift + P and select Preferences: Color Theme and pick the theme
Make changes to themes/dark.json
Create a feature branch and a pull request against main branch.