I am not really sure of how you trade grey stocks. Rocket probably knows this better as I have never even tried. The only thing I have seen is you will see a notation on the pinksheets.com under foreign stocks so I would think some of the grey stock quotes are here too.
PLEASE NOTE: This is a foreign Pink Sheets or Grey Market security. The trade information for this security is available only at the end of the trading day. Best Bid and Ask reflect prices between 8:00am and 4:00pm EST, after these hours the best Bid and Ask at 4:15pm is shown.