Styling of horizontal line in PDF invoice template

Hi,

I’m trying to add style for a horizontal line added to the PDF invoice template.
I’ve added the line using standard <hr> tag and then used e.g. <hr style=”border: 2px solid blue”>, unfortunately this doesn’t work. I also added multiple versions of CSS styling code for hr {} to “styling” tab for invoices but they seem to have no effect on the line. The line always shows as a black horizontal line but I don’t know how to change its style. Can you advise how to make it thicker and e.g. in blue color, please?
Thanks.