Since I heard about green addresses, maybe these are the same type of wallet starting with the prefix 3
In my knowledge segwit address and green address are same, but there is an only difference of prefix that starts with "bc1" and "3" respectively.
I guess he meant
GreenAddress [Bitcoin Wallet] not
Green address.
GreenAddress is a wallet like any other wallets and is not a type of Bitcoin addresses.
This wallet supports segwit addresses that enable you to send using lower fees.
The type of segwit address that supports called "P2SH type" [starting with the number 3]. In addition to many features that make it the best as a wallet for Android and desktop.