Examine source code of Simple Carbon

{
  "theme": {
    "images": {
      "theme_frame": "simple.png"
    },
    "colors": {
      "frame": "#878787",
      "tab_background_text": "#878787"
    }
  },
  "version": "2.0",
  "name": "Simple Carbon",
  "manifest_version": 2,
  "description": "I used a part of the new Steam community site to make this, basically it fits perfect with Steam community and a dark style to Firefox. The only thing I did was take a Steam community image and make it into a persona."
}