JSFiddle - React, Tailwind, and code Playground

HTML

<div ng-app ng-controller="MyCtrl">
    <ng-form name="myForm">
<div ng-class="{ 'error-select': myForm.lead.$error.required}"><span>Leader</span></div>

<select ng-model="lead" name="lead" 
  ng-options="leader.user_id as leader.user_display_name for leader in leaders" 
 
  ng-required="true"></select> 

<div ng-class="{ 'error-select': myForm.own.$error.required }"><span>Leader</span></div>

<select ng-model="own" name="own" ng-options="own.user_id as own.user_display_name for own in owns" ng-init="own = credentials.user_id" ng-required="true"></select> 
    </ng-form>
</div>

CSS

.error-select {
    color: blue;
}

JavaScript

function MyCtrl($scope){
    $scope.leaders = [
                    {"user_id":1,"user_display_name":"11"},
                    {"user_id":2,"user_display_name":"22"}
                  ];
    //$scope.credentials=$scope.leaders[0];    
}