How can i change the font-color of a toolbar programmatically?

It's possible to change the background-color, if i set the background-image to none and apply a color, see exmaple:


But if i change the font-color like in the following snippet nothing happens?


I am using a Pagingtoolbar where you can see some text like "Pageof 2" which should be white.

Thanks for your help in advance.