Which call to action section are you targeting, 1 or 2? We have 2 CTA sections in Integral Pro.

To change the button color in Call to Action 1 use the following CSS code,

.calltoaction .btn-primary {
background-color: #f5bd47; border-color: #f5bd47;

Copy and paste this code into the Custom CSS field of the Custom Code section in Integral Options Panel.