var count = 0;
var color = ['green', 'red', 'blue', '#0e6290', 'black'];
function getColor()
{
    count++;
    if (count >= color.length)
    {
        count = 0;
    }
    return color[count];
}
function SetColor()
{
    Ext.select("a.colorchange").setStyle({ color: getColor() });
}

Ext.onReady(function()
{
    Ext.TaskMgr.start({ run: SetColor, interval: 1000 });
})