Different Custom Icon for Link Hover?

Hi,

I’m using custom icons in a floating share toolbar, and they’re working great, but I’m having trouble getting the styling to work as I want.

I’d like the styling to match the styling in my main navigation menu. Specifically, when a user hovers over a white icon, I’d like that icon to be replaced by a blue icon.

To give an idea of what I’m aiming for, my site URL is below.
http://www.highermathhelp.com/

If it were a simple link and I could see the HTML, a basic image swap wouldn’t be difficult. However, I don’t yet understand how this plugin works under the hood (haven’t learned javascript or php yet).

Thanks!!

https://ww.wp.xz.cn/plugins/add-to-any/