Thanks for getting back to me!
I added the exact code in custom.css but it did not change the appearance of the box. (I didn’t substitute the correct hex yet to avoid too many variables). Am I adding it in the wrong place?
Here’s an exact cut and paste:
Add your custom styles in this file instead of style.css so it
is easier to update the theme. Simply copy an existing style
from style.css to this file, and modify it to your liking. */
/* GLOBAL STYLES
Add styles beneath this line that you want to be applied across your entire site */