Do you mean the html object 'Button' because then I don't think it's possible. You can make your own with a Sprite and Text object on top of it, and the Text you can customize as much as you want.
Thanks, I figured out that if you uncheck "Auto font size" it makes the text in the button a little bigger. I ended not using that anyways and making a Sprite with a Text object ontop of it like you said.
Built in buttons suck for many reasons - you should make your own ^.^
Thanks, I ended up making my own button. I definitely agree that they should make buttons more customizable eaiser. For example, they should make it so you can eaisly select a font size and a background for the button.