text color on text dropdown in main menu

Hi there,

The dropdown on the menu at the menubutton ‘Werkwijze’ shows different font color’ when your are on the particular page.

So i would like to know how i can change the text color of the current page from white into black.
So the text of the dropdown menu may always be black.

I used the following CSS:

.header_color .main_menu .menu ul li a {
color: black;
}

.header_color .main_menu .menu ul li a:hover {
background-color: red;
}