Examine source code of Mosaic Rainbow Gradient

{
  "name": "Mosaic Rainbow Gradient",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "rainbow pixel theme.png"
    },
    "colors": {
      "frame": "rgba(229, 230, 232, 1)",
      "tab_background_text": "rgba(0, 0, 0, 0.6)",
      "toolbar": "rgba(255, 255, 255, 0.25)",
      "bookmark_text": "rgba(97, 0, 0, 0.8)",
      "toolbar_field": "rgba(255, 255, 255, 0.5)",
      "toolbar_field_text": "rgba(201, 32, 32, 0.5)",
      "tab_line": "rgba(255, 196, 0, 0.2)"
    }
  }
}