You can change the color schema, but you can't set the colors in FM charting. FM Charting came out in 2010 and hasn't been updated since then that I can tell. It was pretty good in its time, but showing its age. What I do is use the Google Charts API and take the FM data and put it in a web viewer. You'll need to know HTML as well as learn the charting API. If you happen to know HTML, it's not that hard to do. I know there are some options like using 360 Works Charts plugin. I haven't used it, but that is an option too and probably a little easier than the Google Charts API. And there are other charting APIs out there too.
Thanks Taylor, let's hope FM Charting gets updated to allow this type of chart!