PrimeNG dropdown colored red after change

Question

I'm using PrimeNG's p-dropdown. The options are an array of labels and a value. Every time after a change it is colored red at bottom.

Before selection, it looks like this:

After selection, it looks like this:

HTML code:

<div>
    <span class="md-inputfield">
        <label class="floatPlaceHolder">{{schema.description | translate }}</label>
        <p-dropdown [disabled]="schema.readOnly==true?true:false" appendTo="body" [formControl]="control" [options]="schema.oneOf"
           [autoWidth]="false" appendTo="body" [filter]="schema.oneOf&&schema.oneOf.length>5"></p-dropdown >
    </span>
</div>

Typescript Code:

   "oneOf": [
            {
                "value": 0,
                "label": ""
            },
            {
                "value": 4,
                "label": "A"
            },
            {
                "value": 2,
                "label": "B"
            },
            {
                "value": 1,
                "label": "C"
            }
        ]