Examine source code of Lemon Grayscale

{
  "name": "Lemon Grayscale",
  "manifest_version": 2,
  "version": "3.0",
  "theme": {
    "images": {
      "theme_frame": "1x1.png"
    },
    "colors": {
      "frame": "rgba(41, 41, 41, 1)",
      "tab_background_text": "rgba(170, 170, 170, 1)",
      "toolbar": "rgba(34, 34, 34, 1)",
      "bookmark_text": "rgba(170, 170, 170, 1)",
      "toolbar_field": "rgba(68, 68, 68, 1)",
      "toolbar_field_text": "rgba(170, 170, 170, 1)",
      "tab_line": "rgba(0, 0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{44c927d9-1e00-45de-97e9-1784d6e402c9}"
    }
  }
}