OK, I'm confused. Where is the carpet green? Looks brown/gold/whatever to me. The dash is green, yes, but not the carpeting.
What's the definition of normal? Do you mean was it a combination of colors that could have been ordered from the factory? I don't know. There were far fewer "option packages" back then, meaning that you could pick and choose each option as you went down the list. It wouldn't surprise me that a green dash/brown carpet combination could have been ordered. HOWEVER, it looks to me that the carpet is not original. It's bunched up and wrinkled in the foot area of the passenger front seat, right in front of the left front corner of the seat on the driver's side, on the kick panel on the passenger side, and on the transmission hump in the rear (see the two photos immediately above). All of this looks to me like a mediocre effort at installation of an aftermarket carpet. If it IS aftermarket, then all bets are off as to originality as whoever did it could have chosen any color he wanted.
Unless the installer found a used one. But then, in that instance, were they too cheap to dye it before installing it? A chocolate brown on both the carpet and the dash would've made the car more appealing and less cobbled-together.
Who would want to install a used carpet? Especially one for a 47 year old car? Where did the used carpet come from? Another 47 year old Riviera? Who would want to put that in their car? It's already worn out. It's already been cut. It probably smells to high heaven. And if you add in the cost of cleaning and dyeing it, how much less would it be than a new one? Also, the carpet in this car looks new. There are no wear spots at all that I can see. In fact, it looks like it was installed yesterday. This plus the fact of the wrinkles here and there suggest a new carpet installed by an amateur.
You'd be surprised just how cheap car sales people can be, how cheap anyone is, tripping over a dollar to save a dime. I've put used carpets in cars that were not worn at all, but were different colors. The '77 Pinto wagon I had, I couldn't afford a new carpet, and I looked high and low for a good-condition red one, but nope, not a chance, not anywhere across the country. I then lucked into a black one, perfect condition, but I didn't change the color for cost reasons, and when I traded it, the guy I traded it to didn't mind it.
It's a trick of the light. From one direction, it definitely has a greenish tint. From the other direction, it's clearly tan. Tan makes sense as that's the carpet color.