Changing the colour of number of pictures in a product carousel

Site URL: https://chloeberland.com/

Hello everyone! 

I have a question and hope one of you can help me out.

When my site is in mobile, the arrows don't show on a product carousel (which I know is normal), but instead there's a white number of pictures on the upper right corner. My problem is that most of my pictures have white backgrounds, and it's impossible for mobile users to know that they can swipe to see other pictures. Do you happen to know what little chunk of custom CSS I can add to change that number's color? 

Thank you so much in advance and take care! 
Chloé 

I’ve included a pic so you all can know which number I’m talking about