Change the header background on blog posts only

Hi! I am using an adaptive header which I can make work on my regular pages but on my individual blog posts (when you click into them), I am not able to add a colored section above the post to change the background of the header. Is there some code that I could use to change the color of the header on only the blog post pages?

I would like the color to be: #506F53

Site https://mustard-seabass-es9w.squarespace.com/

PW: girard

TIA!!!!

This worked brilliantly @Web_Solutions! Thank you! 

Follow up question, would there be additional code to make the navigation links and button white?

42 minutes ago, Celeste_Woodside said:

This worked brilliantly @Web_Solutions! Thank you! 

Follow up question, would there be additional code to make the navigation links and button white?

Replace the previous code with the code below. 

.collection-65a98643cc08f52bbfa21f35 header .header-announcement-bar-wrapper {
    background-color: #506f53 !important;
    .header-nav-list a{
        color: #fff !important;
    }
    .header-actions-action a.btn {
        background: #fff !important;
        color: #000 !important;
    }
}

You are awesome! Thank you SO much for your help @Web_Solutions!!

Can I ask one more follow up question?  If I wanted to do this on another page how would I do it? I.e. the 'about' page? @Web_Solutions

20 minutes ago, Celeste_Woodside said:

Can I ask one more follow up question?  If I wanted to do this on another page how would I do it? I.e. the 'about' page? @Web_Solutions

Change the previous code with the code below. 

.collection-65a98643cc08f52bbfa21f35, .collection-65a9569875a7f7122d266533 {
  header .header-announcement-bar-wrapper {
    background-color: #506f53 !important;
    .header-nav-list a{
      color: #fff !important;
    }
    .header-actions-action a.btn {
      background: #fff !important;
      color: #000 !important;
    }
  }
}

@Web_Solutions So that still has the header fixed on the blog post page but didn't change the about us page....