This is multiplied by having layouts within tabs that may also have validation errors. The snippet below is by no means perfect, nor certain to cover every case of layout / repeater / tab / etc, but it is a starting point that you could work with:
jQuery(".acf-error-message").closest(".layout").find(".acf-fc-layout-handle").css("background", "red");
You’d need to get it to fire as a part of or after the ACF validation adds the error code into page.
