I don't know how to explain this bug exactly, but I will provide details on how to reproduce it and a screenshot...
Navigate to: CPanel>Manage Categories>New
Click on Color Picker, this is what I see:
[attachment=0:13nti283]<!-- ia0 -->color picker.jpg<!-- ia0 -->[/attachment:13nti283]
To me it does not appear to be rendering on-screen properly, but you can choose most of the colors (the picker appears to render behind the WYSIWYG editor so you can not select all of the colors that you see).
Just thought I would let you know...
Andrew