Need to change menu color on Blog page

I can’t seem to override the menu font color on the blog page. I have it set to white for the home page, but have changed it to black on all other pages using the code below. It worked on all other pages, but the blog page and the post pages. Any help would be greatly appreciated. Thanks!

    .page-id-14 #mainnav ul li a {
        color: black;

Hello there,

You can use .blog and .single-post class names.

    .blog #mainnav > li > a,
    .single-post #mainnav > li > a {
      color: black;

The code above will only change parent menus.