Add this to the scss file and it will work.
#g-mainbar a {
color: #205ca4;
&:hover {
color: #000000;
}
}
To add custom style sheet to Gantry 5 Framework please follow these instructions:
docs.gantry.org/gantry5/tutorials/adding-a-custom-style-sheet
or if you want to add them in the Page Settings:
docs.gantry.org/gantry5/configure/page-settings#custom-css-js