Hello,
I have tried to change the button border color through the settings menu by editing "Colors" but have had no luck. I was only able to change the button background color but the border color remains the same. Is there a way to easily do this?

It depends on the Application theme you are using, but for the Breeze theme the button border is derived by blending the Button Text and Button Background colors. (other Application themes usually use more of a shadow effect lightening the top borders and darkening the bottom borders)