How to change color of label of Gtk::RadioButton

["Volosatov Alexander" <rope-walker yandex ru>]

When you setup Linux or Windows on left side of window
you can see steps you should do to install it.
And I try to write such class:
in left top corner - name of step with radioButton or CheckButton,
and in left bottom corner - description of active step.
for active step i wand to do , for example, green color of *button label, and for not active step - red. How to do this? (change color of label)
Please help.

when i complit write some of this class, i'll send it to maillist.