Examine source code of Simple Black

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Best Dark Theme",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0.75)",
      "toolbar_text": "rgba(255, 255, 255, 0.75)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(150, 150, 150)",
      "toolbar_field": "rgba(19, 18, 18, 0.5)",
      "toolbar_field_text": "rgba(255, 255, 255, 0.75)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(0, 0, 0)",
      "popup_text": "rgba(255, 255, 255, 0.75)",
      "button_background_active": "rgb(0, 0, 0)",
      "button_background_hover": "rgba(255, 255, 255, 0.25)",
      "frame_inactive": "rgb(0, 0, 0)",
      "icons_attention": "rgba(255, 255, 255, 0.75)",
      "icons": "rgba(255, 255, 255, 0.5)",
      "ntp_background": "rgb(15, 15, 15)",
      "ntp_text": "rgba(255, 255, 255, 0.5)",
      "popup_border": "rgba(255, 255, 255, 0.75)",
      "popup_highlight_text": "rgb(255, 255, 255)",
      "popup_highlight": "rgba(255, 255, 255, 0.25)",
      "sidebar_border": "rgba(255, 255, 255, 0.75)",
      "sidebar_highlight_text": "rgb(255, 255, 255)",
      "sidebar_highlight": "rgba(255, 255, 255, 0.25)",
      "sidebar_text": "rgba(255, 255, 255, 0.25)",
      "sidebar": "rgb(255, 255, 255)",
      "tab_background_separator": "rgb(255, 0, 0)",
      "tab_loading": "rgba(255, 255, 255, 0.75)",
      "tab_selected": "rgba(255, 255, 255, 0.25)",
      "tab_text": "rgb(255, 255, 255)",
      "toolbar_bottom_separator": "rgba(0, 0, 0, 0)",
      "toolbar_field_border_focus": "rgba(255, 255, 255, 0.5)",
      "toolbar_field_border": "rgba(0, 0, 0, 0)",
      "toolbar_field_focus": "rgba(0, 0, 0, 0)",
      "toolbar_field_highlight_text": "rgb(0, 0, 0)",
      "toolbar_field_highlight": "rgba(255, 255, 255, 0.5)",
      "toolbar_field_separator": "rgba(0, 0, 0, 0)",
      "toolbar_field_text_focus": "rgb(255, 0, 0)",
      "toolbar_top_separator": "rgba(0, 0, 0, 0)",
      "toolbar_vertical_separator": "rgba(0, 0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7e7b078a-bd7e-4ace-9aae-b0560e1d3e01}"
    }
  }
}