1968 Solar Red (aka Matador Red on Chevy)
and Red Interior
1968 Pontiac color code "R" is solar red. That same year, Chevy called it matador red and Olds and Buick called it scarlet red.

The correct paint, as used by GM, for the  1968 Firebird is acrylic lacquer. Urethanes and clearcoats all more durable, easier to find and look "deeper" and beautiful but not correct.
Several years ago DupliColor offered a touch-up paint mixed to solar red.
Solar red is identified by DuPont as 4948-LH
Ditzler (PPG) as 71634 Rinshed-Mason as A-1997F
I was able to locate acrylic lacquer but it's becoming difficult to find.
Red Interior
The following interior colors are recommended with solar red:
Black - 253, 269, 272, 259
Red - 252, 258
Parchment - 262, 275, 273, 260
Vinyl Dye
The red interior is documented by Pontiac as
medium red. I used YearOne M30 color vinyl dye for touch-up.
Interior Paints
The upper dash and speaker area is 0% gloss
burgundy. DuPont 9201-LM, Ditzler 71486, Rinshed-Mason 165B55R

The remaining interior is 30% gloss
regimental red. Dupont 9366-LH, Ditzler 71591, Rinshed-Mason 167B51R
One paint chart also shows an additional red shade: 
dark red 30% gloss Ditzler (PPG) code 71589
The dash, door and dash assist bars on mine are burgundy. I know of no dye available for the color.
A fellow 1st gen Firebird enthusiast has found a solar red match in a urethane:
PPG Deltron 2000 DBC3192H Matador Red is a basecoat/clearcoat system. It may look deeper than the factory finish but the color is reported to be a match.  I would have this product applied by a professional shop because any exposure to isocyanates in the paint are highly dangerous health hazards. Read about isocyanates at:
CDC-NIOSHA
Today touchup solar red paint is available from Tower Paint in both lacquer and enamel.
Hosted by www.Geocities.ws

1