Looking at the source code for automobile-book it's already in there, but isn't displaying ads for some reason. The javascript includes "google_alternate_color = "ffffff";" which is forcing it to white under the banner. The google search box is working.
Look in index.php and a few lines below the <body> tag you should see the code to change. If it's not there, it's going to have in its place some type of file include - something like <? include("ads.php") ?>. If it says that look for that file and amend it.
For the arcade look for a file like ads.tpl, sponsor.tpl or some such thing. Much like the other website.
If you still can't find it send me the files and I can look for you.
And, um, that arcade website code is atrocious.