The problem isn't with Illustrator, or MacOSX, it's with your Printer and Paper. The Printer has Black, Cyan, Magenta and Yellow Inks. By Combining different proportions of the different Inks, it can Achieve every Colour Under the Rainbow, and Black. The problem is, When mixing Pigments, like Printer Ink, it is Physically Impossible to obtain white. This is the Main reason why Paper is usually White. It is also the reason why the Paint Mixer at your local Hardware Store always starts with a White Base, and adds pigments until he gets the right colour.
Printing on Brown Paper immediately restricts the amount of Colours you can obtain, because every colour is going to be tinged Brown.
Essentially, Illustrator and MacOSX are printing out White, Your Printer is putting out no Ink, so it thinks it's printing out white, but the problem is that the white is tinged brown.