Welcome to your VS Code Extension

What's in the folder

This folder contains all of the files necessary for your color theme extension
package.json - this is the manifest file that defines the location of the theme file and specifies the base theme of the theme
themes/Panda Extended-color-theme.json - the color theme definition file

press F5 to open a new window with your extension loaded
open File > Preferences > Color Themes and pick your color theme
Open a file that has a language associated. The languages' configured grammar will tokenize the text and assign 'scopes' to the tokens. To examine these scopes, invoke the Inspect TM Scopes command from the Commmand Palette (Ctrl+Shift+P or Cmd+Shift+R on Mac) .

you can relaunch the extension from the debug toolbar after making changes to the files listed above
you can also reload (Ctrl+R or Cmd+R on Mac) the VS Code window with your extension to load your changes
When editing workbench colors, it's easiest to test the colors in the settings under workbench.colorCustomizations. When done, run the Generate Color Theme From Current Settings command to generate an updated content for the color theme definition file.

The token colorization is done based on standard TextMate themes. Colors are matched against one or more scopes. To learn about what scopes are used where, check out the TextMate documentation and the Scope Naming documentation from Sublime.
A great place to examine themes is here.

To start using your extension with Visual Studio Code copy it into the <user home>/.vscode/extensions folder and restart Code.
To share your extension with the world, read on https://code.visualstudio.com/docs about publishing an extension.