Predefined Custom Colors Are Not Saved

Issue description

After adding custom colors to a field, these colors are not saved as pre-defined when adding custom colors to another field. 

Reproducing the issue

Scenario

1. Open any SAP Business One document form.
2. Choose any field in the form, and via right-mouse click, choose coresuite customize → Color field.
3. Adjust the color of your choice and via 'Add to Custom Colors', add it to the Custom colors. 

4. Confim by clicking on OK.
5. Choose another field in the form, and via right-mouse-click, choose coresuite customize → Color field. 

Actual results

The predefined custom color is not available in the Custom Colors section.

Expected results

The predefined custom color is available for reuse in the Custom Colors section.

Cause

Limitation.

Reference

Coresuite-Customize #591