Changing Look and Feel of buttons in OR Designer

How can I change the text size on a button?
Is there a CSS file somewhere that I can edit?

I'm not aware of any way to change the default font / size / colour.

The solution I use is to create bespoke images for each button.

The advantage of this is that you can create round buttons by using the transparency feature. (Or any shape you like)

Another way is to not use the button text but put a label in front of it, that gives you some control over font size and color.