Backgrond Color ThemeMagic

Hi,
I am slowly getting used to Joomla, installed T3 blank + Purity III but whenever I want to change any colors with the ThemeMagic it just shows me that little orange triangle with the exclamation mark in it... Colors are changed when pressing the preview button, but that´s it. I cannot save those changes to my page...
What do I do wrong?
Thanks in advance for the help