You can allow patterns under Printable Color Section. For enabling follow the below steps.
Login to Backend
Navigate to the Product Configurator ➤ Manage Printable Colors, you will get the list of the printable colors.
Here you can view a list of printable colors, navigate to the action column.
Now the color you want to allow the pattern, click on the Edit button on the Action column.
After that, you will be redirected to the Edit printable color page here you can see the selected color details.
Now scroll down to Is pattern allowed option and Enable the toggle option. Further, upload the pattern image by clicking on the Upload button.
After the configuration click on the “Save” button‘.