Do not try to match the colours you see on your screen. You have to go by the numbers.
THE 1970 AMC EXTERIOR COLOUR LINE UP
When American Motors Corporation started accepting orders as early as October 4, 1969 for their 1970 supercar - THE MACHINE, it was only available in one exterior decor format: Red, White, Blue and Beige. All of the first one thousand Machines were to be painted that way. After January 1st any of sixteen colours could be ordered.
1970 AMC PAINT FINISHES
Shown are the Electric Blue Poly which was used on the 1970 Rebel Machine as well as the colour line up for the Matador Machine in the 1971 model year.
As of May 26, 1969 there were 14 colours offered. The Machine paint scheme was not among the colour offerings listed.
So there were the 14 colours with the three 1969 Big Bad Colours - Green, Blue and Orange added later. That brings the total to 17.
But B6 - Electric Blue - 1971 - was an exterior colour and is included in the Parts book as an exterior colour for the 1970 model year. That gets us to 18.
The next exterior colour added was Shadow Black for the hoods and scoops of the solid colour Machines. That brings us to 19.
The Phantom colour is Gray P-81 was listed in 1970 and 71 - bringing us to 20.
Personally I've never heard of a Gray Machine. But any of the the rest of the Mix for 1970 could have been painted gray. Possibly it was a popular fleet colour.
After 1971 AMC changed all of the colours and their designations and went with an almost completely new palette.