Examine source code of Black theme

{
  "name": "nnnn",
  "manifest_version": 2,
  "version": "3.0",
  "theme": {
    "images": {
      "theme_frame": "Gb.png"
    },
    "colors": {
      "frame": "rgba(3, 3, 3, 1)",
      "tab_background_text": "rgba(199, 255, 189, 1)",
      "toolbar": "rgba(89, 89, 89, 0.7)",
      "bookmark_text": "rgba(212, 255, 204, 1)",
      "toolbar_field": "rgba(0, 0, 0, 0.86)",
      "toolbar_field_text": "rgba(230, 255, 224, 1)",
      "tab_line": "rgba(0, 0, 0, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1c1a1b96-1de0-4737-87ec-ebf64a2dc5b7}"
    }
  }
}