ColorListBox control looks by default like on the picture below. It allows user to select one or multiple colors from available list. List can contains only main colors, extended set of colors, and cusom one.

ColorListBox control(widget)

Although you can change properties of individual items(colors) in Form Builder, these changes will be lost by default. To store it you have to either add or delete any item. This action will convert control into custom one and all changes to individual items will be preserved during save, load, and export process. The control remains custom one untill you change one of the properties which changes the list of colors. They are HasStandardColors, HasExtendedColors, and HasNoneColor.