GLCD dynamic font change

Hi there, I wanna make a menu, so I need to change the font from BLACK to WHITE and opposite, can you tell me figure out that ?

Use the invert command.

I don't see this function in documentation ?!

http://www.arduino.cc/playground/Code/GLCDks0108 There is a lot of invert references in this page.

well, I dont have rect, I have text :?