Custom CSS: Menu text change hover color

Hey there, I don't know what I'm doing wrong, but it seems like I can't change the hover color of the menu. When I tried to change the background-color it worked perfectly:

.nav-menu li a:hover
{
    background-color: #0000FF;
}

But I only wanted to change the text color. So I tried:

.nav-menu li a:hover
{
   color: #0000FF;
}

Which does not work at all. What am I doing wrong? Can you please help me? Link to my site: https://sostegisch.com/ Thanks in advance, Alex