Examine source code of CAS mascot

{
  "theme": {
    "images": {
      "theme_frame": "CAS_Persona_Head_v2.3.jpg"
    },
    "colors": {
      "frame": "#ccdde5",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "CAS mascot",
  "manifest_version": 2,
  "description": "The popular CAS mascot now issued as a Firefox Persona skin"
}