Blank or Black Text
From Second Life Wiki
In the last release the setting file may have become corrupted, if you tried to save a color change in preferences or make a customised swatch in the color picker.
In the preferences window the colors would turn black on relog, this has been fixed in this release but this may cause problems still, the easiest way to fix this is to logout and delete the 'settings.xml' file, or do a complete uninstall and reinstall of the client.
The 'settings.xml' file can be found in these directories depending on the operating system:
1) Windows: C:\Documents and Settings\username\Application Data\SecondLife\user_settings\
2) Mac: username/Library/Application Support/SecondLife/user_settings/
3) Linux: ~/.secondlife/user_settings/ (Note: '~' is the user's home directory and is typically: /home/username)