Creates a signing theme defined by your settings. A customized signing theme is a signing theme
designed by your organization using, for example, your corporate branding.

Sample request:

POST /cs-account/signingThemes
{
  "default": {
    "color": {
      "signatureButton": "#CAEA19",
      "error": "#3B48B5",
      "signatureSticky": "#5940C3",
      "warning": "#BE5718",
      "primary": "#CAEA19",
      "optionalSignatureButton": "#CAEA19",
      "info": "#2E74B2",
      "success": "#1B7445"
    }
  }
}