ng-class Add/Remove

<div ng-class='{"myClass": isOpened}'></div>

/* add class */
.myClass-add{
    transition: color 1s linear;
}

.myClass, .myClass-add-active{
    color: blue;
}

/* remove class */
.myClass-remove{
    transition: color 1s linear;
}

.myClass-remove-active{
    color: blue;
}