I have a piece of code like below

<div class="footer o_standard_footer">
    <div class="text-center" style="border-top: 1px solid black;">
        <ul class="list-inline mb4">
            <li t-if="company.phone" class="list-inline-item">Phone: <span t-field="company.phone"/></li>
            <li t-if="company.email" class="list-inline-item">Email: <span t-field="company.email"/></li>
            <li t-if="company.website" class="list-inline-item">Web: <span t-field="company.website"/></li>
            <li t-if="company.vat" class="list-inline-item"><t t-esc="company.country_id.vat_label or 'Tax ID'"/>: <span t-field="company.vat"/></li>
        </ul>

        <div name="financial_infos">
            <span t-field="company.report_footer"/>
        </div>

        <div t-if="report_type == 'pdf'" class="text-muted">
            Page: <span class="page"/> / <span class="topage"/>
        </div>
    </div>
</div>

I just want to change the style="border-top: 1px solid black; to style="border-top: 1px solid lightgray;"  Normally i would inherit the whole div and change as per requirement but i wanna know is there any efficient method to inherit the above code to change just the border?

Also I have another code like below

<template id="report_invoice_document">
    <t t-call="web.external_layout">
        <t t-set="o" t-value="o.with_context(lang=lang)" />
        <t t-set="address">
            <address t-field="o.partner_id" t-options='{"widget": "contact", "fields": ["address", "name"], "no_marker": True}' />
            <div t-if="o.partner_id.vat" class="mt16"><t t-esc="o.company_id.country_id.vat_label or 'Tax ID'"/>: <span t-field="o.partner_id.vat"/></div>
        </t>

I don't know to inherit the t  because it has no id and i'm really confused as to what should i mention in xpath, someone tell me how to inherit the t field to modify the address widget?