Hello,
Thanks for the detailed feedback.
Using not valid attributes/values when importing HTML/CSS may return a warning as your case details when using a not valid color. The lastest release of phpdocx handles this specific case to avoid the PHP warning.
phpdocx 12 includes the following change that sets an empty color if the variable is not set in the _get_border method:
$color = $this->__get("border_" . $side . "_color");
if (!isset($color['hex'])) {
$color['hex'] = '';
}
Regards.