Feature Requests can be submitted here: http://www.filemaker.com/company/contact/feature_request.html in order for them to be seen by the FileMaker personnel who decide what features will be included in future versions.
The Active button can be a different color. If you need each Inactive button a different color, then create a new button bar with one button and change the color of the one button. You can have more than one button bar each with a different color.
You would think that would have been in the default behavior of the button bar, I guess it was just an oversight.
Maybe the work around will help.
The problem is that the work-around nullifies the main advantage of having a button bar: the ability to hide buttons depending on certain events letting you basically have a dynamic bar. Until a few days ago, I used that system in FM12 and one of the reasons I asked for an upgrade was the button bar because it offered these benefits so it's a shame this was not implemented. The colours aren't crucial but we're used to certain color codes (green for orders, blue for item data, purple for delivery data, etc.) so it makes more sense to keep these colours.
I'll follow the link Phil posted and make it a request. Thanks for the help.