Not sure about actually restoring the colour, but I used a few of the usual interior cleaners, Meguires being one. If you still find it, Eagle One Spot Remover is excellent. I also used some household bleach on some parts, but that's another story!
Interior dye is available from the usual suppliers (Ecklers, Corvette Central etc) if you find that the colour doesn't come back.
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Stephen J Irons
Corvette Club France
CCCUK Lifetime Member
Corvettes of Southern California
NCM Family Member
Red Corvettes Have More Fun!