Add this to your custom css page. The below is what I used to hide a sidebar region on NODE 508. Replace the 508 with your NodeID and whatever you would like to change in the additional selectors.
.page-node-508 #right-sidebar{
display:none;
}
You can use this css to do any kind of theming on a specific node. :)
Another example is
.page-node-508 #title-wrapper h1 {
color: red;
}
This make the title on that node red but no other nodes. :)