Magento 2: How to Change Product Title Font and Color

You'll want to go into the templates from the admin area: Marketing --> Email Templates

... and then you'll want to edit a template using inline CSS formatting.

HTML for email is a whole different animal. Due to security restrictions, you usually cannot load external stylesheets, so everything needs to be done in-line.

Here's a quick code example:

<p><span style="font-family: Arial, Helvetica, sans-serif; font-size: 14px; color: #000000;"><strong>Thanks for your recentl order from our store.  We are thrilled to be shipping it out to you today.</strong></span></p>

I hope this helps...

You are missing the etc/di.xml which is necessary to rewrite setTabTitle() method.

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <preference for="Magento\Review\Block\Product\Review" type="Custom\Review\Block\Product\Review" />
</config>

And your Custom\Review\Block\Product\Review.php should look like this:

<?php

namespace Custom\Review\Block\Product;

class Review extends \Magento\Review\Block\Product\Review
{
    /**
     * Set tab title
     *
     * @return void
     */
    public function setTabTitle()
    {
        $title = $this->getCollectionSize()
            ? __('The Reviews %1', '<span class="counter">' . $this->getCollectionSize() . '</span>')
            : __('The Reviews');
        $this->setTitle($title);
    }
}