Follow to Theme Settings > Appearance > Fonts > Navigationand choose the color, fontname and size for all the navigation elements: item title, hover, dropdown, dropdown hover. There’s a font line height option as well, so you can control the vertical distance between item lines. Don’t forget to save changes.
To customize your navigation buttons hovers’ color, please, follow to Theme settings > General
And choose Theme Color in the General tab. You’ll get the theme color changed as well as menu items hovers’ one – buttons’ and some basic elements’ and links’ color, unless you’ve changed them separately.