Hi there,
the borders are added using CSS – go to Customizer > Additional CSS. There are a few CSS rules – the two you will want to change i have commented below:
.woocommerce ul.products li.product a img,
.woocommerce div.product div.images img {
padding: 3px;
border: 1px solid rgba(0, 0, 0, 0.1); /* This rgba color for borders around products */
box-sizing: border-box
}
.separate-containers .inside-article,
.separate-containers .sidebar .widget,
.site-header,
.main-navigation:not(.slideout-navigation),
.site-footer {
border: 1px solid rgba(0, 0, 0, 0.08) /* This RBGA value for the main containers */
}