How can I remove the HTML/CSS background-color from the body?

WEB TMS WEB Core
8

As I said, I do not know who and why this is generated.
But I would be very interested.

I manage first by deleting the "style" in this SPAN.

procedure TfrmKundeSelect.WebFormDOMContentLoaded(Sender: TObject);
begin
  console.log( document.body.firstElementChild.getAttribute( 'style'));
  document.body.firstElementChild.setAttribute( 'style', '');
  ...