Do ground screws used to to ground metal boxes have to be listed & do they have to be green?

No. I think they are very handy to use and I installed my share of them, but they are not a requirement. you do have to bond the boxes (250.148), but in my opinion as long as you do not use a sheet-metal screw, you are fine.

Just to add to Ryans answer, for the people that might not of crossed this before.
250.8 prohibits the use of sheetmetal screws for grounding.

I will add that many times people get hung up on 250.126 Identification of Wiring Device Terminals.

This article says the ground screws on devices must be green.

Article 100

250.126 has nothing to do with the screws used for grounding anything else.