It was pretty easy to do as I too disliked the dark theme.
A little differently but same idea.
I opened Preferances/Customization/ Themes in SPlat and saved the default Tungsten as " My Tung" using the theme editor.
I then copied that from the Sonar Themes folder to the Cakewalk Themes folder found in Cakewalk Content as scook says above.
I opened CbC and loaded " My Tung" which now showed in the list in Preferences.
I didn't have to change the file extention as the "My Tung" was already sth.