Is it possible to have different header style blog titles in different categories?

I assume that any post belongs to only one category.

Create respective CSS classes, e.g. ‘news-header’ and ‘mindset-header’, and use following code inside the loop:

<?php
// get post categories
$categories = get_the_category();
// get single category
$category = $categories[0];
// echo header with category class
echo '<h2 class="' . $category . '-header">' . get_the_title() . '</h2>';