Change social buttons color separately

Hi everyone! I am trying to customize the Sketch theme, and I would like to change the color of the social media buttons.
By default in this theme they are all of the same color (orange), but I want to use the Facebook, Twitter and Google+ social buttons with their most used colors (the blue for Facebook, and so on).
¿Can you help me around with the additional CSS I shoud use for that?
Thank you