Whats the differance between R4 red and R6 red colors

Let me try and decode this

L= dart
M= Class?
23=2 door hard top
P=340
9=1969
B= hamtrac
E55=?
D21= 4 speed
R4=performance red
R4= ?
L2X=?

It's pretty orange. If you parked next to a red car it looked orange.

Do you have any pictures of the car. Sounds like you had my dream car. So R4 sounds like the color I want ?
Thanks for helping