Examine source code of peak meter fading

{
  "theme": {
    "images": {
      "theme_frame": "peak_meter_fading_h.png"
    },
    "colors": {
      "frame": "#ff0000",
      "tab_background_text": "#ffffcc"
    }
  },
  "version": "2.0",
  "name": "peak meter fading",
  "manifest_version": 2,
  "description": "background pattern peak meter tiled with gradient from dark gray to transparent"
}