Changing the Color of Menu Tabs

Can someone please help me figure out how to change the color of the menu tabs at the top of my site? I’d like the selected tab to be one color (white) and the non-selected tabs to be another color (pale yellow). I’ve been reading forums all night but haven’t found a way to do this.

My site is https://angelaslibrary.com. I’m using the Misty Lake theme and host with BlueHost. Thanks in advance for your help!