This Placeholder Body code comes in two parts:
  1. The Search Form HTML.
    1. This is generated from https://ddg.patdryburgh.com
      1. In other words, you can do this yourself.

    2. It creates a Search button that you can customise to your specific site colours.
    3. It uses DuckDuckGo and your inputted site URL, or Top Level Domain (TLD).
    4. You can stop at this point.

  2. A JavaScript enhancement.
    1. Basically, this replaces the inputted TLD with the one whose page it finds itself on.


The Code:
Code:
<form method="get" id="ddgSearch" action="https://duckduckgo.com/">
    <input type="hidden" name="sites" value=""/>
    <input type="hidden" name="k7" value="#e0dada"/>
    <input type="hidden" name="k8" value="#222222"/>
    <input type="hidden" name="k9" value="#00278e"/>
    <input type="hidden" name="kx" value="#20692b"/>
    <input type="hidden" name="kj" value="#f8e71c"/>
    <input type="hidden" name="kt" value="o"/>
    <input type="text" name="q" placeholder="Search…" aria-label=""/>
    <button type="submit">Search</button>
</form>


<script>
  var TLD = window.location.protocol + "//" + window.location.host + "/";
  oFormObject = document.forms['ddgSearch'];


  oFormObject.elements['sites'].value = TLD;
  oFormObject.elements['q'].setAttribute('aria-label', 'Search ' + TLD);
</script>
This code replaces your sites.value and aria-label with the TLD detail.

Say, you were happy with my choice of house colours then you would just add this code to a Placeholder and the job is done.
You could tweak the colours manually or match with your current values of Palette from Image:
  • k7 - Background Colour.
  • k8 - Link Colour.
  • k9 - URL Colour.
  • kx - Text Colour.
  • kj - Header Colour.

If you do not want a Search Button showing, change the code to <button type="submit" style="visibility: hidden">Search</button>

Why?
Say, you add SSH and access your website through SSL, https://, then you don't need to do a thing.
Do remember all web search engines need to have crawled your site at some point so this works best for an enhancement to an existing site.
It uses DuckDuckGo as it does not track your end-user, which is only fair.

Acorn