W3.CSS - Pro
Version 4 comes with a professional version: W3.CSS Pro.
The pro version is identical to the standard version except for it has no colors defined.
The pro version is designed for using themes or other colors supplied by the developer.
The pro version can be downloaded from: https://www.w3schools.com/w3css/4/w3pro.css
W3.CSS Pro Colors
With W3.CSS pro you can define your own colors:
Example
<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://www.w3schools.com/w3css/4/w3pro.css">
<!-- Colors here -->
<body>
<!-- Content here -->
</body>
</html>
You can define your colors inline with a <style> tag:
Example
<style>
.w3-amber{color:#000!important;background-color:#ffc107!important}
</style>
Or you can load your own themes: