This first one is a bit small, but you can definately make out the paint demarcation lines. I believe that this is actually a civilian-owned T-38 that is painted in the Thunderbirds' scheme.
http://mk23.image.pbase.com/u35/marauder61/small/40447507.resizeIMG_3639.jpg
The next picture may do you more good than the first one. I posted the website that I got the pic from below, as it has multiple angle shots of the Thunderbird T-38's that may come in handy..
http://www.vaq136.com/owatonna/index.html
**** You know what? I just noticed that there is a difference between the paint scheme in the first photo and the paint scheme in the bottom photo(s). Now I am wondering which one is correct! ****