Examine source code of Mixed Marbles

{
  "name": "Mixed Marbles",
  "manifest_version": 2,
  "version": "5.0",
  "theme": {
    "images": {
      "theme_frame": "MarbledHCustom.jpg"
    },
    "colors": {
      "frame": "rgba(103, 116, 171, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(103, 116, 171, 0)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(103, 116, 171, 0.05)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{276668b6-def5-4a2d-8b47-803bf8251009}"
    }
  }
}