Examine source code of RE:Studio Space

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#f2f2f9",
      "tab_background_text": "#6e6e7a"
    }
  },
  "version": "2.0",
  "name": "RE:Studio Space",
  "manifest_version": 2,
  "description": "We like things clean. Classy up your Firefox browser with this minimal theme. Gentle shadows and loads of white space."
}