Changing Mail messages' colors (colours)

Hi,

Being new to Macs I'm trying to get to grips with Mail and am generally finding it pretty good.

I've figured out how to use Preferences to select a single color to highlight related messages but I wondered if it's possible for different threads to be highlighted in different colors. Even random colors would be good, just a way to see at a glance the various threads I have running.

Thanks for any help you may have!
Patrick