Can't change button color under image on product page

Hi,
I have a product page in editor x which shows images of the product for sale. My problem is with the buttons beneath the image that allow the user to see multiple images for that product. They aren’t visible against the black background of my website. The images below show the buttons visible when I change the background color to white, and invisible when I keep the background color as black.
screen
Does anyone know how to change the colors of these buttons?