Colorful square in hero web part

Hi,

our end users are really observant and have found out that on these web site (https://www.microsoft.com/en-us/microsoft-365/blog/2017/06/27/sharepoint-communication-sites-begin-rollout-to-office-365-customers/) Microsoft presents hero web part with a little bit specific desing as you can see on the screenshot. Do you have any idea how to get the colorful square to hero web part? I have verified all hero web part settings but I am not able to figure it out...

Thank you for your tips,

Mirek