design-themes/theme_odoo_experts/views/snippets/s_quotes_carousel.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>

<template id="s_quotes_carousel" inherit_id="website.s_quotes_carousel">
    <xpath expr="//div[hasclass('s_quotes_carousel')]" position="attributes">
        <attribute name="class" remove="carousel-dark" separator=" "/>
    </xpath>
    <!-- Carousel item #1 - filter -->
    <xpath expr="//blockquote" position="before">
        <div class="o_we_bg_filter bg-black-50"/>
    </xpath>
    <!-- Carousel item #2 - filter -->
    <xpath expr="(//blockquote)[2]" position="before">
        <div class="o_we_bg_filter bg-black-50"/>
    </xpath>
    <!-- Carousel item #3 - filter -->
    <xpath expr="(//blockquote)[3]" position="before">
        <div class="o_we_bg_filter bg-black-50"/>
    </xpath>
</template>

</odoo>