Changing font color of "Subject", "From", "Date" etc. in folders

Hey all. I have a dark theme installed for Thunderbird. Until today, the font color of messages in the various folders was a decent shade of blue on my black background. It was easy to see, and easy on the eyes (I have vision problems and white kills me). Today, something happened and the color of these items changed to bright white for new messages and a muted white for read messages. I'm wondering how to change the color of these items. I'm familiar with CSS style sheets. Can Stylish or Greasemonkey be installed in Thunderbird? Or, is there another way to do this. The only part I want to change is the information for emails. The rest of the font colors are fine, so just the "subject", "from" and "date".