Examine source code of Opera Dark Mode v2

{
  "name": "Opera Dark Mode v2",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "greyUntitled.png"
    },
    "colors": {
      "frame": "rgba(25, 28, 31, 1)",
      "tab_background_text": "rgba(170, 170, 170, 1)",
      "toolbar": "rgba(57, 69, 81, 1)",
      "bookmark_text": "rgba(220, 220, 220, 1)",
      "toolbar_field": "rgba(10, 10, 10, 0.49)",
      "toolbar_field_text": "rgba(220, 220, 220, 1)"
    }
  }
}