Yes, you can use your custom CSS for this, in the dashboard under Customize > CSS.
The code that defines the rollover colour is this bit:
You can try adding this in your custom CSS to turn the coral colour a light grey, tweaking the shade as you like.
background: #d1dde0 !important;
This is a great post which talks about how to find CSS selectors – you might want to check it out:
We also have a guide to some CSS basics:
I can attempt it with CSS if that’s the way to go…I’m just learning wordpress and CSS, but it’s really fun
The thing about CSS is the more you learn, the more fun it becomes. :-)
Let me know how it goes, and if you need help with anything else, feel free to start a new thread!