Examine source code of porple gradient

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "porple gradient",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/0.png"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "center top"
      ],
      "additional_backgrounds_tiling": [
        "repeat-x"
      ]
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(30, 31, 41)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(30, 31, 41)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(0, 0, 0, 0)",
      "popup": "rgb(30, 31, 41)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(30, 31, 41)",
      "button_background_hover": "rgba(117, 54, 188, 0.5)",
      "icons": "rgb(255, 255, 255)",
      "ntp_background": "rgb(30, 31, 41)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_border": "rgba(0, 0, 0, 0)",
      "sidebar_border": "rgb(66, 67, 75)",
      "sidebar_highlight_text": "rgb(255, 255, 255)",
      "sidebar_highlight": "rgb(117, 54, 188)",
      "sidebar": "rgb(30, 31, 41)",
      "tab_selected": "rgb(30, 31, 41)",
      "toolbar_bottom_separator": "rgba(0, 0, 0, 0)",
      "toolbar_field_border_focus": "rgb(117, 54, 188)",
      "toolbar_field_border": "rgba(0, 0, 0, 0)",
      "toolbar_field_focus": "rgb(30, 31, 41)",
      "toolbar_field_highlight": "rgb(117, 54, 188)",
      "toolbar_field_separator": "rgba(0, 0, 0, 0)",
      "toolbar_top_separator": "rgba(0, 0, 0, 0)",
      "toolbar_vertical_separator": "rgb(66, 67, 75)",
      "tab_loading": "rgba(0, 0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a6d84afa-a4e6-4569-9557-ec6380032de2}"
    }
  }
}