Green Lantern is now a light theme.
Liberation Sans regular 11 is a very pretty Font for this Theme here, in my Sense.
If you wish to use a very fine green Light around you Windows, go into the System Settings:
> Workspace Appearance > Window Decorations > Oxygen // Configure Decoration > Shadows > Active Window Glow > Inner Color: #00C000
Quassel use by default the global KDE Color Scheme and it is possible to tune it fine in its Settings.
If you use KMail, i recommend you to change the Color Settings from it in its Settings; Configure KMail, Appearance, Colors and use costum colors. Edit that one for unread Messages from Blue into White (#FFFFFF)
Suggestions are very welcome;