angle size

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/jsxgraph/0.97/jsxgraphcore.js"></script>
<link rel="stylesheet" href="http://jsxgraph.uni-bayreuth.de/distrib/jsxgraph.css">
<div id="box" style="width: 500px; height: 500px;"></div>

JavaScript

var board = JXG.JSXGraph.initBoard('box'),
    index = 0,
    colors = ['red', 'green', 'blue'],
    p = board.create('point', [2, 0], {color: colors[index]});

p.on('down', function () {
  alert();
    index = (index + 1) % colors.length;
    p.setAttribute({color: colors[index]});
});