Change Tab Color and Text

I have looked everywhere can't locate an answer. I would like to change the BG color and text the default is very hard to see, please point me to the right area/file. See the image below.

/assets/css/bootstrap.min.css

.btn-warning {
   background-color: #f0ad4e;
   border-color: #eea236;
   color: #fff;

Thanks Brian, I located the text in that file should I change the text or just add the above to the end of the file with the colors I want? Again thanks for your help.

Thanks Brian, I located the text in that file should I change the text or just add the above to the end of the file with the colors I want? Again thanks for your help.

by default, you can't use a custom.css in the admin templates - I think that currently only works for client templates.

so two options - you could add your custom changes to the end of admin/templates/blend/style.css - that should allow you to modify the admin styling without the need to modify the assets folder content... just watch out for changes to style.css during any future WHMCS updates.

or you could create a custom.css file in your admin/template/*templatename* folder and add your customised css styling in there... and then add the action hook below to the includes/hooks folder and call it 'admincssstyle.php'...

<?php

function admin_custom_css_hook($vars) {

   $currenttemplate = $vars['template'];
   $head_return = '';
   $head_return = '<link href="templates/'.$currenttemplate.'/custom.css" rel="stylesheet" type="text/css" />';
   return $head_return;
}
add_hook("AdminAreaHeadOutput",1,"admin_custom_css_hook");

the hook will add a link to your custom.css file in the head and should remain working after any WHMCS updates to the template... or until WHMCS decide to add the option themselves!