gtk: indicate a button should be pressed

Question

What's the best way to indicate on a GTK interface that a button should be pressed / to "highlight" the button? The use case is that I have a set of checkboxes representing various settings, but for them to take effect, they must be submitted to a server. I want to indicate that the currently checked settings have not been sent to the server, by, for example, highlighting the Submit button to be red.

I tried messing with the button style to change its color conditionally, but I ran into problems there.

Answer 1

Perhaps you could disable the button (so that it "greyed out") until all the checkboxes have been set or whatever... This is quite a common approach.

Answer 2

You could set the button's label to be bold when there are changes to be submitted:

button.get_child().set_markup('<b>Submit</b>')