Color disappear on a page when I hide navigation links

I want to hide certain navigation links on a certain pages, but when I code into the page-header-code-injection, all the colors on that page disappear. (buttons, shapes, and backgrounds)

What code are you using?

Hi! I'm using the below style:

<style>
  .header-nav-item:nth-child( # ) {
      display : none;
        }
  <style>

The problem is probably the error in the closing style tag, it's missing the /

Should be this:

<style>
  .header-nav-item:nth-child( # ) {
    display : none;
  }
</style>

Leaving HTML tags unclosed correctly is normally the problem when pages suddenly stop rendering correctly.

Thanks!