Examine source code of Mattetheme

{
  "name": "Matte",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "February-2021-2560X1440.jpg"
    },
    "colors": {
      "frame": "rgba(0, 0, 0, 0)",
      "tab_background_text": "rgba(0, 0, 0, 1)",
      "toolbar": "rgba(252, 252, 252, 0.53)",
      "bookmark_text": "rgba(82, 0, 0, 1)",
      "toolbar_field": "rgba(135, 38, 0, 0.45)",
      "toolbar_field_text": "rgba(107, 0, 0, 1)",
      "tab_line": "rgba(184, 31, 0, 0.41)"
    }
  }
}