Hi Rob.
I believe the colour is either BSA Flamboyant Red Candy or Maroon Candy for your '69 Rocket 3. I have experience of using the former. For this, the original paint scheme was to use a basecoat of metallic silver on top of which is the Flamboyant Red lacquer on top of which is the clear coat. However, when I painted my B25T and B50T in Flamboyant Red, I used a metallic gold basecoat which was considered better than silver at the time.
You can get either of the original colour schemes (with silver basecoat) from RS Paints.