body_class() function

Hello,

https://quirm.net/2009/08/07/changing-headers-with-wordpress-body_class/

I’ve been working from the above link to try and colour code sections of my site. got it working on the ‘search’ class and the ‘blog’ class but cant seem to make it happen for individual pages. Specifically this page which is meant to have the same yellow background as the About menu section. would be really grateful if anyone could give me some direction on this?

Thomas