The bad news is that an update today over wrote our old fieldset coding, and now fieldsets can no longer have custom colors. >:[
The good news is that we can re-add an alternate fieldset code that will! (I will do that tomorrow when I am more awake.)
The bad news is that either way, you're going to have to edit those posts to fix it. D:
The good news is that we added several new bbcodes today with really awesome styling tools that'll make up for that inconvenience. >> Maybe.