Examine source code of Opposites

{
  "theme": {
    "images": {
      "theme_frame": "opositeh.jpg"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#4164c4"
    }
  },
  "version": "2.0",
  "name": "Opposites",
  "manifest_version": 2,
  "description": "Reflections using GIMP transform tool with invert gegl tool"
}