How to change the text colour of a button??

Hi

Is there any way to change the text color of a button? 

I have tried numerous methods to change the Font colour of buttons. But non worked. I have used in the custom css file under btn Font-color: #000; and also tried Text-color: #000; What am I missing? What is the best way to do this? I need to change the button text color to black. Using the Monte Black theme..

Please help