Make a list of xs:enumeration appear in <menuChoices/> XML element without repeating them

Question

In my schema, I have a colorName enum list, a <color name="one_of_colorName"/> element, and a <colorsUsed/> element with a unique list of <color/>s used, thus:

<!-- color name list -->
<xs:simpleType name="colorName">
  <xs:restriction base="xs:string">
    <xs:enumeration value="red"/>
    <xs:enumeration value="green" />  <!-- etc. -->
  </xs:restriction>
</xs:simpleType>

<!-- color element, just go with the col: namespace -->
<xs:element name="color">
  <xs:complexType>
    <xs:attribute name="name" type="col:colorName" use="required"/>
  </xs:complexType>
</xs:element>

<!-- unique list of colors used -->
<xs:element name="colorsUsed">
  <xs:complexType>
    <xs:sequence>
      <!-- let's hold off on max which must be the length of the color name list -->
      <xs:element ref="col:color" maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>

  <!-- enforce unique color name in the list -->
  <xs:unique name="uniqueColorName">
    <xs:selector xpath="col:color"/>
    <xs:field xpath="@name"/>
  </xs:unique>
</xs:element>

Question 1: I would like to have the <colorChoices/> menu populated with all the colors in the color name list, without repeating them, either in the schema or the XML file, along these lines:

<xs:element name="colorChoices">
  <xs:complexType>
    <xs:all>                         <!-- need the name list, one each -->
      <xs:element ref="col:color"/>  <!-- ?? what how ?? -->
    </xs:all>
  </xs:complexType>
</xs:element>

Question 2: I have a working solution, but would be nice to have: In <colorsUsed/> element, can I restrict maxOccurs=length_of_colorName_list?

Thanks for the answer or the link to an existing answer, which I can't seem to find.

Answer 1

List all <color> choices whose type is xs:string, in the menu element <colorChoices/> and get rid of the enum list. Then enforce uniqueness of <color name="???"/> in both <colorChoices/> and <colorsUsed/>. If you know of a better answer, please update. Thanks.