Examine source code of Nothing but Fields

{
  "theme": {
    "images": {
      "theme_frame": "Landscape.jpg"
    },
    "colors": {
      "frame": "#9e0808",
      "tab_background_text": "#c42b2b"
    }
  },
  "version": "2.0",
  "name": "Nothing but Fields",
  "manifest_version": 2,
  "description": "The green fields of home"
}