This plugin adds a node to the adminbar clarifying the current environment setting if not production.

environment-notifier.php

<?php

/*
 * Plugin Name: Environment Notifier
 * Plugin URI: http://github.com/georgestephanis/environment-notifier/
 * Description: This plugin adds a node to the adminbar clarifying the current environment setting if not production.
 * Author: George Stephanis
 * Version: 1.0
 * Author URI: http://wpspecialprojects.wordpress.com
 */

add_action( 'admin_bar_menu', function( $wp_admin_bar ) {
	if ( ! function_exists( 'wp_get_environment_type' ) ) {
		return;
	}

	$environment_type = wp_get_environment_type();
	if ( 'production' === $environment_type ) {
		return;
	}

	$wp_admin_bar->add_node( array(
		'id'     => 'environment',
		'title'  => ucwords( $environment_type ),
		'parent' => 'top-secondary',
		'meta'   => array(
			'class' => "environment-{$environment_type}",
		)
	) );

	wp_register_style( 'environment-notifier', null );
	wp_enqueue_style( 'environment-notifier' );
	wp_add_inline_style( 'environment-notifier', '#wp-admin-bar-environment > .ab-item { background-color: #800; }' );
} );

More details on wp_get_environment_type() -- https://make.wordpress.org/core/2020/08/27/wordpress-environment-types/