That actually depends on the printer you are using rather than the software.
You have to go to the print menu, choose separations and then print only the separations you want, but on the printer RIP (our directly in indesign via the printers PPD plugin, on the "Printer" option), you have to activate an option commonly know as "Combine Separations"... If you do it, you'll have the separations in the right color, otherwise it will always turn out black and white.
Other than that, i can only remeber of printing to a PDF in separations, open the PDF in Photoshop, and color all the diferent separations in the right color, but i think that will be a real pain...
Hope this helps, and sorry for my bad english
PS: Separations preview is only for visual check... It won't affect printing in anyway.
Good luck
