I can add more than one color and it can only be black.

There should be a color button to access the color pellet to the left of the red box.

on inspecting the html I get this

<div class="control-group  umb-prevalues-multivalues__add color-picker-preval">
        <div class="umb-prevalues-multivalues__left">
            <input name="newColor" type="hidden" autocomplete="off">
            <label for="newColor" val-highlight="true" class="ng-binding highlight-error">#000000</label>
            <input name="newLabel" type="text" ng-model="newLabel" focus-when="false" class="umb-property-editor color-label ng-pristine ng-valid ng-empty ng-touched" placeholder="Label" ng-show="labelEnabled" aria-hidden="false" aria-invalid="false">
        </div>
        <div class="umb-prevalues-multivalues__right">
            <button class="btn btn-info add" ng-click="add($event)"><localize key="general_add" class="ng-isolate-scope">Add</localize></button>
        </div>
    </div>

On a project where to does work it looks like this

<div class="control-group  umb-prevalues-multivalues__add color-picker-preval">
        <div class="umb-prevalues-multivalues__left">
            <input name="newColor" type="hidden" autocomplete="off" style="display: none;" value="#ec7432"><div class="sp-replacer sp-light"><div class="sp-preview"><div class="sp-preview-inner" style="background-color: rgb(236, 116, 50);"></div></div><div class="sp-dd">▼</div></div>
            <label for="newColor" val-highlight="false" class="ng-binding">#ec7432</label>
            <input name="newLabel" type="text" ng-model="newLabel" focus-when="true" class="umb-property-editor color-label ng-pristine ng-untouched ng-valid ng-empty ng-hide" placeholder="Label" ng-show="labelEnabled" aria-hidden="true" aria-invalid="false">
        </div>
        <div class="umb-prevalues-multivalues__right">
            <button class="btn btn-info add" ng-click="add($event)" style=""><localize key="general_add" class="ng-isolate-scope">Add</localize></button>
        </div>
    </div>

This Line appears to be the broken line

<input name="newColor" type="hidden" autocomplete="off" style="display: none;" value="#ec7432"><div class="sp-replacer sp-light"><div class="sp-preview"><div class="sp-preview-inner" style="background-color: rgb(236, 116, 50);"></div></div><div class="sp-dd">▼</div></div>

Both projects are version 8.6

I have compared the Umbraco folder and both contents are exactly the same.

Has anybody come across this