sometimes it is a bit greenish but mostly brown with darker brownish stripes and reddish/orangish pectoral fins.
the lfs said they ordered them in off their suppliers brackish list so im pretty sure they are brackish.
I had a look through my Baensch Atlas, and didn't see anything that matched closely. You could try this site, to see if you can find a picture, or maybe post on the forums: http://gobiidae.com/
just an update:
no one on gobiidae.com could pinpoint what they are exactly but they are in my 180gal brackish tank and doing fine so far. they seem to be strictly herbivore as all i see them do is scrape algea off the rocks and glass.
i will update if i find out what goby they are or if anything changes.