It is not rare but not as common as black.
I had seen many a green interior too-but most got swapped out for black or white.

My friend's 1970 A66 Challenger (340/727,3.23 SureGrip) car.
His Dad bought it new off the showroom floor.
After a 25 year wait,the car was completely restored.
Pics showing it October 2007 when completed.