Change Button Colours

Site URL: https://www.fasxfis.com/our-services

Hi there, 

Would anyone know how to change the 3 buttons to different colours in CSS? 

The page is https://www.fasxfis.com/our-services

Thanks in advance

Add to Design > Custom CSS

/* Our services buttons */
div#block-e6469ce507e32bb2a3b7 + .row .button-block a {
    background: green;
}