JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/knockout/knockout-2.2.1.js"></script>
Profit:
<span id="profitPercentage"
    data-bind="text: profit, style: { color: (profit()<10)?'Red':'Green' }">
</span>

   <input id='inpName' data-bind="text: profit" />

CSS

body
{
    font-family: Arial;
}

JavaScript

// Style Binding

// Our viewmodel with observables
function viewmodel() {
    //self = this;
    this.profit = ko.observable($('#inpName').val()); 
}

// Runs at document load
$(document).ready(function(){
    // Create an instance of the viewmodel
    var myViewmodel = new viewmodel();
    
    // Bind the instance to the view
    ko.applyBindings(myViewmodel);
});