Scroll-down Button Color – Header Media

Hi, I have my site in Zubin Pro and my background Header Media image is white. The scroll-down button is also set to white, so the downward arrow for this button does not show up on my site. How can I change the color of the scroll-down button to black? Would custom CSS work for this? If so, please let me know if it is possible to use CSS to make the scroll-down arrow black... My site URL is here. Thank you in advance!