Change Color of Before/After Button Backgrounds for Slider

Hi, I am loving the Before / Slider feature! However, I am using it for my branding/website design business and sometimes the default purple box behind the “After” button clashes with the before/after color palette of my design images. I’d love to be able to choose what the “Before” and “After” button background colors are, separately. AKA choose the “Before” color and then choose a different “After” color.