Examine source code of Breeze Dark

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#31363b",
      "tab_background_text": "#eff0f1"
    }
  },
  "version": "2.0",
  "name": "Breeze Dark",
  "manifest_version": 2,
  "description": "This simple theme makes Firefox match the Breeze Dark theme in Kubuntu with Plasma 5."
}