Examine source code of Cool theme - ct

{
  "name": "Cool theme - ct",
  "manifest_version": 2,
  "version": "2.0",
  "theme": {
    "images": {
      "theme_frame": "Wall_001 (1).jpg"
    },
    "colors": {
      "frame": "rgba(89, 18, 18, 1)",
      "tab_background_text": "rgba(244, 252, 0, 1)",
      "toolbar": "rgba(89, 18, 18, 1)",
      "bookmark_text": "rgba(244, 252, 0, 1)",
      "toolbar_field": "rgba(104, 107, 75, 1)",
      "toolbar_field_text": "rgba(244, 252, 0, 1)",
      "tab_line": "rgba(41, 18, 18, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a1b08fcc-84c7-4dba-a4d1-27ef060086ae}"
    }
  }
}