Examine source code of testing(1)

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "test",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-034-e0dfa84411058d2e5627f19f1ea501ca.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgba(31, 0, 56, 0)",
      "toolbar_text": "rgb(49, 255, 229)",
      "frame": "rgb(36, 0, 72)",
      "tab_background_text": "rgb(25, 255, 226)",
      "toolbar_field": "rgba(54, 58, 89, 0.95)",
      "toolbar_field_text": "rgb(140, 255, 206)",
      "tab_line": "rgba(189, 0, 255, 0.81)",
      "popup": "rgba(28, 0, 57, 0.68)",
      "popup_text": "rgb(7, 255, 238)",
      "button_background_hover": "rgba(184, 7, 255, 0)",
      "frame_inactive": "rgb(233, 0, 255)",
      "icons": "rgb(113, 188, 255)",
      "tab_background_separator": "rgba(180, 0, 255, 0)",
      "tab_selected": "rgba(184, 7, 255, 0)",
      "tab_text": "rgb(0, 247, 255)",
      "toolbar_field_border": "rgba(0, 0, 0, 0)",
      "tab_loading": "rgba(189, 0, 255, 0.81)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b758d264-cc7b-4859-82ba-b6f5e5571ecd}"
    }
  }
}