simplei

The module works very much like Environment Indicator module with a minimal approach. It requires Drupal core's Toolbar (Drupal 8+) or Admin menu (Drupal 7) modules and changes the color of the Toolbar as you like.

Version 2.x now supports Gin theme and Drupal 10.

It is a simple module that does one thing, to color the Toolbar. It has no configurable user interface. All you need to do is place a line in settings.php such as,

// Drupal 7
$conf['simple_environment_indicator'] = 'DarkRed PRD';

// Drupal 8+
$settings['simple_environment_indicator'] = 'DarkRed PRD';
// or
$settings['simple_environment_indicator'] = '#fff/#666 PRD';
// or
$settings['simple_environment_indicator'] = '@PRD';
// accessible colors with #access
$settings['simple_environment_indicator'] = '@PRD#access';

The web color name(s) or hex value(s) are followed by the environment name. You can specify background color only (foreground is white) or foreground/background colors. If you use @ sign with the environment name, the predetermined color will be used.

Drupal 8+ version supports anonymous users who don't normally have access to Toolbar.

$settings['simple_environment_anonymous'] = TRUE;

If you do not like the default rendering of the environment indicator, you can
set to a string instead of a boolean value, such as,

   $settings['simple_environment_anonymous'] = "body:after { 
     content: \"STAGE\" ;
     position: fixed;
     top: 0;
     left: 0;
     padding: 0.1em 0.5em;
     font-family: monospace;
     font-weight: bold;
     color: #fff;
     background: brown;
     border: 1px solid white; }";

You would not want to display the indicator for anonymous users in production
environment, but nothing will stop you if you have a reason to do so.