I remember one of the 599s in prologue had a Burgundy interior, not in GT5 though.
Interior options are nice, but id rather have a FM4 style "showroom" function where we can explore the beautiful cars PD have modelled up close, and manipulate them with the analogs for zoom\movement. Its too hard to get a good look at the Interior in GT5, the replay angles only compliment certain cars, others have that ridiculous "handbrake" cam or focus on the driver.
Without this i couldnt care what color the interior is, if i cant even see it 90% of the time.
And when we buy a car with a certain color interior (R8 audio V10 in blue with red interior for example), when the car is painted the interior resets to a black or generic color interior.