Examine source code of Before you ...

{
  "name": "Before you ...",
  "manifest_version": 2,
  "version": "3.0",
  "theme": {
    "images": {
      "theme_frame": "BeforeYou-Header.jpg"
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0)",
      "toolbar_field": "rgba(0, 0, 0, 0)",
      "toolbar_field_text": "rgba(253, 249, 232, 1)",
      "frame": "#b6a03a",
      "tab_background_text": "rgba(253, 249, 232, 1)"
    }
  }
}