You can also change the version string in the "Areas\Contents\WebResources.config", but the file also need to restart the website to take effect.
The file generated the like is : "Kooboo\Web\Mvc\WebResourceLoader\MvcExtensions.cs".
My suggest, if you want to avoid restarting the site, do not change the raw file. You can create a css patch, then include the css file after the system css including in the view.
Regards,
Jifeng Huang
Kooboo Team
Microsoft ASP.NET MVP