How do I change the background color of only one page in squarespace?

Site URL: https://pufferfish-porpoise-7ata.squarespace.com/

I am using the Bedford template and when I have changed the body background color, it changes it the the same on every page. How do I change the background color of only one page in squarespace? I have tried with various custom codes/css without any luck. I am new to Squarespace so I am probably just being a novice 😕 🙂 Link to page: https://pufferfish-porpoise-7ata.squarespace.com/ 

And the password to get access to my site is: Userfriendly

Thanking you in advance.

Can you share link to page in question? We can check easier.

https://pufferfish-porpoise-7ata.squarespace.com/ and the password is: Userfriendly 

Is that what you need?

You mean homepage?

Add to Home > Design > Custom CSS

.homepage div#siteWrapper {
    background: red;
}

Ah, sorry for not describing the task well enough. It was this page I needed to do it for and not the frontpage (home): https://pufferfish-porpoise-7ata.squarespace.com/teamet

Add to Home > Design > Custom CSS

body#collection-5ee3906bbff7b11983bc19f2 div#siteWrapper {
    background: red;
}