Technically, there is no way to order stacked columns within each category individually. Each column segment will come in the same order as they are defined in graphs array.
This demo shows how to work around that by automatically converting all graphs to non-stacked, non-clustered floating columns.
It uses AmCharts.addInitHandler() function to define code that executes before chart is initialized. We take this opportunity to examine our graphs, go through data and recalculate their open and close values based on their values, so they look stacked up, but in fact they're not.
Please note that stackByValue setting used in this demo is completely made up for purposes of this demo and is not part of amCharts engine.