Issue

You would like to make some Color customization on subsites in SharePoint 2019, but you are not able to do that.

Reason

Unfortunately, due to a known SharePoint 2019 bug that causes modern pages in SharePoint 2019 subsites to sometimes be displayed using the root site's theme, we have decided to disable Color Palette on subsites in SharePoint. This will prevent inconsistencies and weird behaviors until the SharePoint 2019 bug is fixed.

Solution

The good news is that you can still make your color customization in ShortPoint's theme builder on your root sites, and publish your custom branding.