Changing nav font color only if there's no background image

Site URL: http://www.kindredhomestead.com/blog

My client wants the navigation font color to be white on top of the images she has as the background but some pages are gradient and the white navigation is lost into the background.

I'm looking for some way to either target the font that's on a gradient background or on an image to change the font color.

Here's a link to a page with a background image:

kindredhomestead.com/home

But then a few pages end up like this one:

kindredhomestead.com/blog

Any ideas? I don't want to target each individual page to change it because I'm sure she's going to add and remove pages frequently..

Add this code to Page Header (page where you want to change nav color)

<style>
  .header-nav * {
    color: black !important;
}
</style>

Thank you!!!