How to change GTK+3 label color dynamically

[Rúben Rodrigues <ruben_gr live com pt>]

Hi,

Now i need to change GtkLabel color dinamically, so i thing that i can't 
use Css to do this.. I do this in Gtk2:

gtk_widget_modify_fg(GTK_WIDGET(gtk_builder_get_object(builder,"label")),GTK_STATE_NORMAL, 
&white);

How can i change the color in Gtk3?

Thanks