Examine source code of yellow_theme

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "color theme",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-029-cc9cab928c1799136d18758709e91ecc.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(0, 150, 255)",
      "toolbar_text": "rgb(154, 47, 143)",
      "frame": "rgb(252, 225, 2)",
      "tab_background_text": "rgb(166, 63, 57)",
      "toolbar_field": "rgba(255, 255, 255, 0)",
      "toolbar_field_text": "rgb(255, 241, 0)",
      "tab_line": "rgb(253, 124, 73)",
      "popup": "rgb(236, 220, 249)",
      "popup_text": "rgb(65, 183, 190)",
      "tab_loading": "rgb(253, 124, 73)"
    }
  }
}