Don,

DuPont 2 stage is just as tough as any OEM paint. You can go with their Urathane clear which is the most durable. Since your buddy is an auto body guy he'll know exactly how to formulate the clear. If not done right the clear can be brittle....or too soft...one scratches...the other fractures and flakes off.

Red and Orange are expensive...but both hide body flaws well....
And if your doing Lime Green....be careful of metallics...they are tricky in the line colors.

if everything is primered....then sealed it will be the same color all over. the whole car needs to be primed and sealed at the same time. If not they can gas out at different rates and cause minor color shift. make sure he uses sealer closest to the color you choose. Lime Green....go white sealer....dark colors...dark sealers.

My buddy has been laying down paint since the early 90's....and we use nothing but DuPont and House of Colors on my stuff.

As far as color samples.....your buddy should have a CHIT book if he has the DuPont mixing system....we just paint my boys Junior the new Honda Accord midnight black...it actually has blue pearl and blue mica flake....turned out awesome in the sun.