Examine source code of Night Shadow

{
  "manifest_version": 2,
  "name": "Night Shadow",
  "description": "A theme with a dark color scheme that fully modifies the appearance of Firefox browser far beyond the built-in customization features",
  "author": "Serhiy Guryev",
  "version": "0.5",
  "theme": {
    "colors": {
      "frame": "rgb(12, 9, 10)",
      "frame_inactive": "rgb(12, 9, 10)",
      "tab_text": "rgb(255, 255, 255)",
      "tab_background_text": "rgb(190, 190, 190)",
      "tab_selected": "rgb(50, 50, 50)",
      "tab_loading": "rgb(211, 211, 211)",
      "tab_line": "rgb(37, 37, 37)",
      "toolbar": "rgb(37, 37, 37)",
      "toolbar_text": "rgb(170, 170, 170)",
      "toolbar_field": "rgb(20, 20 ,20)",
      "toolbar_field_text": "rgb(200, 200, 200)",
      "toolbar_field_focus": "rgb(20, 20 ,20)",
      "toolbar_field_border": "rgb(20, 20 ,20)",
      "toolbar_field_border_focus": "rgb(20, 20 ,20)",
      "toolbar_top_separator": "rgb(37, 37, 37)",
      "toolbar_bottom_separator": "rgb(18, 18, 18)",
      "toolbar_vertical_separator": "rgb(170, 170, 170)",
      "icons": "rgb(169, 169, 169)",
      "icons_attention": "rgb(211, 211, 211)",
      "button_background_active": "rgba(255, 255, 255, 0.15)",
      "button_background_hover": "rgba(200, 200, 200, 0.12)",
      "popup": "rgb(20, 20 ,20)",
      "popup_text": "rgb(200, 200, 200)",
      "popup_border": "rgba(255, 255, 255, 0.15)",
      "popup_highlight": "rgb(80, 80, 80)",
      "popup_highlight_text": "rgb(255, 255, 255)",
      "ntp_background": "rgb(24, 25, 26)",
      "ntp_text": "rgb(170, 170, 170)",
      "ntp_card_background": "rgb(40, 40, 40)",
      "sidebar": "rgb(20, 20 ,20)",
      "sidebar_text": "rgb(200, 200, 200)",
      "sidebar_border": "rgba(255, 255, 255, 0.1)",
      "sidebar_highlight_text": "rgb(170, 170, 170)",
      "sidebar_highlight": "rgb(80, 80, 80)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c321b6ce-2283-41f7-8a30-62f9f86aa509}"
    }
  }
}