Barry, I believe that he's talking about the lower racings stripes on '68 GTXs. I don't think anyone can tell you if the colors are the same as I'm not convinced that the colors offered today are really the same as the originals. I have never seen documentation stating what color 3M vinyl was used (or whatever company it was) and whether the vinyl still exists today and is what is being used on the repros.
For the one GTX I have seen with green stripes it doesn't appear that the colors were the same but you have to take into account fading, etc. The blues and reds do look the same in both cars, GTX and Challenger) that I've seen because they are all reproductions. Who knows what the originals should be like.
As for the name ledger paper green, that was coined by Performance Car Graphics. Same with tomato red and peacock blue. Mopar only called them red, blue and green. The GTX stripes that I saw did resemble ledger paper. Very pale green. The Challenger stripes aren't like that. More like a pea soup green to me.
I wish I had original stripe samples of all colors, but alas I don't and doubt that I ever will (of any color).
The only NOS stripes I've ever been offered are T/A ones. I should have bought them, but I didn't want to deprive an owner of a T/A from having the chance.