can i use different background color for single.php ?

This is typically quite possible by editing your stylesheet…but, without posting a site link here, that is about all we could tell you…

single.php
is here:
https://www.aozhou123.com/aozhou123/2012/06/13/%E5%A2%A8%E5%B8%82%E5%AE%B6%E5%BA%AD%E8%A2%AB%E5%A4%9A%E6%94%B6%E9%80%BE3%E4%BA%BF%E5%85%83%E6%B0%B4%E8%B4%B9/

And here is css address:
https://www.aozhou123.com/aozhou123/wp-content/themes/aozhou123/style.css

Your site took so long to check at site scanner, I gave up.

use this will do.

body.single {
background-color:red;
}