It's definitely gray on the website. It isn't gray when I use the WordPress mobile app, though. Could you have clicked on a setting while updating a page and didn't notice it? I remember there being a way to change the font color of the whole site, so maybe you accidentally changed the site that way.

I found this, which looks up to date and may be able to help: https://www.ryrob.com/how-change-font-color-wordpress/ The first section should have what you need.

I haven't done much with WordPress in a while, but I've been working with similar sites while volunteering. Let me know if you need more help.