Examine source code of On a cloudy day

{
  "theme": {
    "images": {
      "theme_frame": "persona_header.png"
    },
    "colors": {
      "frame": "#828282",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "On a cloudy day",
  "manifest_version": 2,
  "description": "Just a quick Firefox fix for those who like cloudy, rainy days for a change."
}