Unable to change the colors of the buttons in the Menu Cart Pop Up

I have the show content cart tab activated so that when you hover over the menu cart icon, a little pop up cart appears. Inside the pop up cart is a view cart button and a checkout button. I have tried to select these buttons and change their colors using css, but I was unsuccessful. I would just like to know how I can change the colors of the buttons so that they aren’t this ugly grey color anymore. It doesn’t match the button colors of my store. Please help!