I strongly recommend your friend identify the tiny scraps of original 99 paint left on the car & take pictures NEXT TO THE IDENTIFIED PAINT CHIP as a reference.

Cameras, computer screens, phones all "distort color" so you need to have some type of body shop paint chip of the identified color right next to the scrap of paint left on the car to positively identify the color. The idea here is that when your phone camera (& screen for that matter) distort the color, at least it will be right next to the paint chip, so they "should" be distorted about the same.

Sorry this sounds weird, but I'm a paint scientist. That would let you identify the original color. 99 paint jobs are rare. Convertibles are rare. Some day, somebody might want to document the car & restore it 100% original and having this paint information with GREATLY increase the value of the car in my opinion.

Hope this helps.