Examine source code of F-Colors

{
  "name": "F-Colors",
  "manifest_version": 2,
  "version": "3.0",
  "theme": {
    "images": {
      "theme_frame": "theme_tab_background.png"
    },
    "colors": {
      "frame": "rgba(237, 125, 125, 0)",
      "tab_background_text": "rgba(3, 105, 95, 1)",
      "toolbar": "rgba(230, 212, 212, 0.66)",
      "bookmark_text": "rgba(0, 0, 0, 1)",
      "toolbar_field": "rgba(255, 255, 255, 0.6)",
      "toolbar_field_text": "rgba(0, 0, 0, 1)",
      "tab_line": "rgba(250, 142, 142, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6778c33-ce06-43c0-9af8-adeba80962ac}"
    }
  }
}