Knockout - Set Radio from TextBox

HTML

<script src="https://github.com/downloads/SteveSanderson/knockout/knockout-2.0.0.js"></script>
<input data-bind="value: userColor disable:true" />
<br/>
<p><input type="radio" value="red" data-bind="checked: formattedColor"/>Red</p>
<p><input type="radio" value="green" data-bind="checked: formattedColor"/>Green</p>
<p><input type="radio" value="blue" data-bind="checked: formattedColor"/>Blue</p>

JavaScript

var viewModel = (function() {
    var me = t
    me.userColor = ko.observable("Red");
    me.formattedColor = ko.computed(function() {
        return this.userColor().toLowerCase();
    }, me);
})();

ko.applyBindings(viewModel);