Examine source code of HU-Firefox_GAMMA

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#39438f"
    }
  },
  "version": "2.0",
  "name": "HU-Firefox_GAMMA",
  "manifest_version": 2,
  "description": "Plain white Theme with Logo of the Humboldt-University of Berlin.\nHeader and Fooder. Text: None."
}