Creating theme in SharePoint 2016

I think what you are looking for is SharePoint Themes.

Themes provide a quick and easy way to apply lightweight branding to a
SharePoint site. A theme lets a site owner, or a user who has designer
rights, customize a site by changing the site layout, color palette,
font scheme, and background image.

More Information here:

SharePoint Themes Overview

Branding SharePoint sites in the SharePoint add-in model