Examine source code of Chromium Dark

{
  "browser_specific_settings": {
    "gecko": {
      "id": "chromium-dark-theme@spacegamedev",
      "strict_min_version": "42.0"
    }
  },
  "manifest_version": 3,
  "version": "1.0",
  "name": "Chromium Dark",
  "theme": {
    "colors": {
      "frame": "#202124",
      "frame_inactive": "#3c4043",
      "tab_background_separator": "#5e5f61",
      "tab_background_text": "#ffffff",
      "toolbar_field_highlight": "#546782",
      "toolbar_field_highlight_text": "#ffffff",
      "toolbar_field_text": "#ffffff",
      "toolbar_field_text_focus": "#ffffff",
      "toolbar_field": "#252629",
      "toolbar_field_focus": "#292a2d",
      "toolbar_field_border": "#00000000",
      "toolbar_field_border_focus": "#458beb",
      "tab_loading": "#458beb",
      "tab_text": "#ffffff",
      "bookmark_text": "#ffffff",
      "tab_selected": "#38393c",
      "toolbar": "#38393c",
      "tab_line": "#00000000",
      "button_background_active": "#454649",
      "button_background_hover": "#454649",
      "toolbar_top_separator": "#00000000",
      "toolbar_vertical_separator": "#5e5f61",
      "toolbar_bottom_separator": "#606164",
      "popup_highlight": "#458beb",
      "popup_highlight_text": "#ffffff",
      "popup": "#2d2e31",
      "popup_border": "#00000000",
      "ntp_background": "#202124",
      "ntp_text": "#ffffff",
      "sidebar_border": "#00000000",
      "sidebar": "#2d2e31",
      "sidebar_text": "#ffffff",
      "sidebar_highlight": "#458beb",
      "icons": "#ffffff",
      "icons_attention": "#ffffff"
    }
  }
}