Normally, the chart displays graphs in the same order as they are defined in chart's graphs array.
This very simply plugin, which uses AmCharts.addInitHandler() call, pre-sorts graphs using their proprietary index property.
AmCharts.addInitHandler(function(chart) {
// Reorder chart graph's based on their "index" value
chart.graphs.sort(function(a, b) {
if (a.index == b.index) {
return 0;
}
return a.index < b.index ? -1 : 1;
});
}, ["serial"]);