Gotta agree with salmon on this one. Can you verify specifically what color (paint code) it is?

Getting back to the question, I'd say as long as you stick to a stock '68 color and its what you want, I don't think it will much matter in the long run. Perhaps a couple percent on price either way, unless you go with some obscure color like Primavera or Cameo. I see those colors sit for sale a LONG time. And make sure the color you pick would have been in combination with the interior and top. (you can see that from PHS)

If you are buying the car to flip it in a year or two, I wouldn't bother. A good repaint, depending on the body shop or if you do it yourself is likely in the range of $3500 to $6000. A full frame off is probably over $20k.

Also keep in mind that current trends frown on red and black cars. I see MANY people walk right by my solar red 'vert to get to the blues and greens these days. But you should do what YOU want, not what the rest of the herd thinks.