require 'gtk'

window = Gtk::Window.new(Gtk::WINDOW_TOPLEVEL)

style = Gtk::Style.new
style.set_font Gdk::Font.fontset_load '-adobe-helvetica-bold-r-normal--18-*'
style.set_fg(Gtk::STATE_NORMAL, 10000, 50000, 60000)
style.set_bg(Gtk::STATE_NORMAL, 65535, 50000, 50000)

Gtk::Widget.push_style style
button = Gtk::Button.new('Hello World')
Gtk::Widget.pop_style

window.add button
button.show
window.show
Gtk.main