In case anyone else got stuck initially as I did (took me a couple minutes to figure out)New Board Themes (available in your user control panel)
Control Panel: ucp.php
Board Preferences: ucp.php?i=373
Edit Global Settings: ucp.php?i=ucp_prefs&mode=personal
"My board style:" seems to default to prosilver so you just change that to other stuff, submit and after it refreshes past the next screen it will take effect.
I'm trying out ProSilver dark now, an interesting new feel for Palladium