Bring back User Activity colors as per 0.4
In 0.4, one could adjust the colors for each user activity message (different colors for join, part, kick, rename, etc.). In 0.5, they have been merged into a single color. This makes it very difficult to tell the difference between messages like joins and quits. Adding another column to the Custom Colors box could take care of this, or it could be presented in a different box, perhaps through another tab/pop-up, and activated by checking a box.
Documenting the stylesheet stuff is an acceptable workaround to this issue, but a less knowledgeable user might still be unable to get this working. Personally, I'd take a slightly fatter settings dialog over less readable chat text.