How do i change the background of a blog post without affecting the entire site ?

I have tried everything (even using chatgpt) and nothing has worked.

When i used the command line in header page injection :

<style>

 #post-id { background-color: #f1f1f1 !important; 

 }

</style>

it changes the colour of the text box and the colour of the rest of the site remains the same?

Im using the Palmera template

help!

Hi,

Can you share link to a blog post? We can help easier