Hover colors break when I change color in theme settings.

The main nav menu, just below the header, when using the 'dark red' base style, is dark red when dropped down, and darker red when I hover over the menu items. When I change the color to my desired shade of red (just changing 'main color', but happens when I change any color) the second 'hover' color stops working.

I have tried many different combinations and it always stops working when I customize the colors. Can anyone tell me why?