Examine source code of green_grass

{
  "theme": {
    "images": {
      "theme_frame": "header_grass.jpg"
    },
    "colors": {
      "frame": "#2e0000",
      "tab_background_text": "#003b09"
    }
  },
  "version": "2.0",
  "name": "green_grass",
  "manifest_version": 2,
  "description": "an ecologic dress for our browser :)"
}