Examine source code of Just plain grey

{
  "theme": {
    "images": {
      "theme_frame": "gp_header.png"
    },
    "colors": {
      "frame": "#292929",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Just plain grey",
  "manifest_version": 2,
  "description": "A simple and plain dark grey persona."
}