How to change the colour of the background in my 404 page but not the header?

[Lsoft]

I am trying to change the background colour to black but nothing else.

Each time I add background html it changes the header also, I presumed my theme was pulling the header in, but I think not, any ideas?

<div class="theme-default-margin">
  <div class="container">	
    <div class="row">
      <div class="col-lg-12 col-12">
        <div class="error-content text-center"><img src="my image soon to come" alt="image" border="0">
          {% if settings.opps_404 %}
          <img src="{{ settings.opps_404 }}" alt="" />
          {% endif %}
          {% if settings.heading_404 !='' %}
          <h4>{{ settings.heading_404 }}</h4>
  
          {% endif %}
          {% if settings.sub_text_404 !='' %}
          <p>{{ settings.sub_text_404 }}</p>
          {% endif %}
          {% if settings.button_title !='' %}
          <a class="theme-default-button" href="{{ settings.button_url }}" data-text="{{ settings.button_title }}" >{{ settings.button_title }}</a>
          {% endif %}
        </div>
      </div>
    </div>
  </div>
</div> 

[Vikas_Chovatiya]

Hi @Lsoft 

Thanks Welcome to the Shopify community!
Please share your site URL,
So I will check and provide a solution here.