How to make the 'X' darker with CSS

Trying to make the 'X' or close sign darker on lightbox mode for an image block, every CSS code I come across is for a gallery or leads to a dead end.

Thank you in advance!

Can you share your website URL and this page?

2 minutes ago, Ziggy said:

Can you share your website URL and this page?

Sorry,

https://www.erinncapko.com/

(all pages are basically set up the same, image was taken from first/main page)

1 minute ago, Ziggy said:

Try adding this to Custom CSS:

.sqs-lightbox-close {
  color:#000000 !important;
}

That is the one! Thank you so much! 

No problem!