Examine source code of color-nostalgia

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "color-nostalgia",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-000-5672c42860d5b06e1058dc477397f3ef.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(205, 200, 175)",
      "toolbar_text": "rgb(68, 68, 68)",
      "frame": "rgb(73, 73, 73)",
      "tab_background_text": "rgb(220, 218, 215)",
      "toolbar_field": "rgb(176, 183, 176)",
      "toolbar_field_text": "rgb(51, 51, 51)",
      "tab_line": "rgb(68, 68, 68)",
      "popup": "rgb(220, 218, 215)",
      "popup_text": "rgb(91, 105, 130)",
      "icons_attention": "rgb(130, 91, 105)",
      "icons": "rgb(51, 51, 51)",
      "sidebar_text": "rgb(34, 34, 34)",
      "tab_loading": "rgb(68, 68, 68)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{05afd878-8bd8-4516-a517-b845e31a1afa}"
    }
  }
}