Examine source code of Dark Concrete

{
  "theme": {
    "images": {
      "theme_frame": "concrete1.jpeg"
    },
    "colors": {
      "frame": "#b0b0b0",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Dark Concrete",
  "manifest_version": 2,
  "description": "this is a simple but striking persona, it's a sharp concrete texture"
}