Color-Code WordPress Pages by Assigned Template

/**
 * Add template-specific CSS classes to Pages admin rows.
 */
add_filter(
	'post_class',
	'alkesh_add_page_template_admin_row_class',
	10,
	3
);

function alkesh_add_page_template_admin_row_class(
	$classes,
	$class,
	$post_id
) {
	if ( ! is_admin() || ! function_exists( 'get_current_screen' ) ) {
		return $classes;
	}

	$screen = get_current_screen();

	if (
		! $screen ||
		'edit' !== $screen->base ||
		'page' !== $screen->post_type ||
		'page' !== get_post_type( $post_id )
	) {
		return $classes;
	}

	$template = get_page_template_slug( $post_id );

	// Identify pages using the default template.
	if ( empty( $template ) ) {
		$classes[] = 'alkesh-template-default';
		return $classes;
	}

	/*
	 * Map exact template filenames to CSS class names.
	 * Replace these examples with your actual template filenames.
	 */
	$template_classes = array(
		'templates/landing-page.php' => 'alkesh-template-landing',
		'templates/contact.php'      => 'alkesh-template-contact',
		'templates/full-width.php'   => 'alkesh-template-full-width',
	);

	if ( isset( $template_classes[ $template ] ) ) {
		$classes[] = $template_classes[ $template ];
	} else {
		$classes[] = 'alkesh-template-other';
	}

	return $classes;
}

/**
 * Apply template-specific colors in the Pages admin list.
 */
add_action(
	'admin_head-edit.php',
	'alkesh_style_page_template_admin_rows'
);

function alkesh_style_page_template_admin_rows() {
	$screen = get_current_screen();

	if (
		! $screen ||
		'edit' !== $screen->base ||
		'page' !== $screen->post_type
	) {
		return;
	}
	?>
	<style>
		/* Default page template: amber */
		.wp-list-table tr.alkesh-template-default > th,
		.wp-list-table tr.alkesh-template-default > td {
			background-color: #fff3cd;
		}

		/* Landing page template: blue */
		.wp-list-table tr.alkesh-template-landing > th,
		.wp-list-table tr.alkesh-template-landing > td {
			background-color: #dceeff;
		}

		/* Contact page template: green */
		.wp-list-table tr.alkesh-template-contact > th,
		.wp-list-table tr.alkesh-template-contact > td {
			background-color: #dff3e4;
		}

		/* Full-width template: lavender */
		.wp-list-table tr.alkesh-template-full-width > th,
		.wp-list-table tr.alkesh-template-full-width > td {
			background-color: #eee5ff;
		}

		/* Other custom templates: light gray */
		.wp-list-table tr.alkesh-template-other > th,
		.wp-list-table tr.alkesh-template-other > td {
			background-color: #f0f0f1;
		}
	</style>
	<?php
}