So, here's my take: I intensely dislike (hate's too strong a word for someone I've never met) TB (Mainly because of what went down with LEE1), so I took it with a grain of salt.
I've been binging Kibbe and Friends, and they actually just released an episode on this:
http://www.themusclecarplace.com/kibbe-and-finnegan/kf-show-165/
The gist is Corndog, one of the co hosts (he also runs the Real General Lee website/Facebook/Instagram page), is a bodyman by trade and says that depending on many different factors, a paint reader can return many variations because it matches the color with a database. Whatever color the paint was sprayed over (T3 Bronze in Lee1's case) can also play a role.
Now, Renaud Valuzet, one of the crew that built a majority of the TV cars (If it's in CA and has the narrow bar, it's 98% likely to be a Valuzet car) told Kibbe at one point they used "Dulux Code 70 Enamel".
Code 70 is the GM color code for 1975 Corvette Flame Red.
I may be messing a bit up, I only listened to it once. But it's worth a listen.
In other words, it's highly unlikely that they specifically went for TNT Express Orange. We'll probably never know unless the guys that built the first 3 Lees ever come out and discuss it (if they're still with us- I don't think I've ever heard who they were, come to think of it).
I've also heard that the first 3 were Hemi Orange, but they didn't like how it showed up on cameras so they switched to Flame Red. The first three may have been repainted Flame Red after Hemi Orange. I don't have a source because I can't exactly remember where I read that.