Examine source code of demonslayer..

{
  "name": "demonslayer..",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "zenitsu-tanjiro.gif"
    },
    "colors": {
      "frame": "rgba(12, 28, 5, 1)",
      "tab_background_text": "rgba(55, 97, 63, 1)",
      "toolbar": "rgba(16, 105, 36, 0)",
      "bookmark_text": "rgba(240, 220, 39, 1)",
      "toolbar_field": "rgba(250, 247, 252, 0.07)",
      "toolbar_field_text": "rgba(21, 92, 163, 1)",
      "tab_line": "rgba(230, 140, 30, 1)"
    }
  }
}