the stand alone pallete picker is not compatible with DW CS6.
It has been integrated into the free tools extension:
free-tools/
You will need to use that version with DW CS6
First, reset the workspace layout in DW:
go to Window -> Work Space layout -> Reset '<your layout name>'
and Delete the Dreamweaver Cache file from the users configuration folder:
common_installation_issues.php
Then uninstall Palette picker from the extension manager and install Free tools.