Examine source code of van-gogh------

{
  "name": "van-gogh",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "LA NOCHE ESTRELLADA, DE VAN GOGH.jpg"
    },
    "colors": {
      "frame": "rgba(0, 0, 0, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(194, 194, 194, 1)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(255, 255, 255, 0.98)",
      "toolbar_field_text": "rgba(179, 170, 170, 1)",
      "tab_line": "rgba(255, 201, 201, 0.02)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b88000e8-bb1d-4f7c-89da-f49e5c2d5625}"
    }
  }
}