Examine source code of Halo 1_2_3

{
  "theme": {
    "images": {
      "theme_frame": "firefoxwebbrowserhalo1.jpg"
    },
    "colors": {
      "frame": "#0009ab",
      "tab_background_text": "#ff9d00"
    }
  },
  "version": "2.0",
  "name": "Halo 1_2_3",
  "manifest_version": 2,
  "description": "just a halo  theme"
}