In order to build a specific Theme you need to run:

grunt --theme=<themename>

Available themes are: default, black, matrix, squares, triangles

Ex. grunt --theme=black

By default the original theme will be built.

If you want to create a new theme:
- Use the themes/default as source material
- Make a copy in themes folder with a new name
- Add your theme folder name on line 237,239 and 242
- And then build as above, with your theme folder/name.

That's it!