CSS for color of icon on a menu

I can change the background color and text color of a primary tabbed menu button using:

.kn-menu .kn-button.is-primary {background-color: #6c8fb3 !important;}

...and I can change to color of the text.
But can't seem to change the color of the icons on those buttons.
Can anyone suggest CSS for this task?
Thanks much

Use the class :

.fa {

  color: your color here;