I loved my bi-color, named Bob, so I understand where you're coming from. Bicolors will eat just about anything once they get established at feeding but try tempting him out with some small meaty morsels. Once he gets used to coming out to feed, he shouldn't be so shy.
I'll bet though, that he's eating algae off the rocks and glass. Mine used to do that all the time. I miss ol' Bob; I lost him when I had a dinoflagellate bloom in the tank.
both blennys are alge eaters maby try some dried nori or seaweed selects and put it in an alge clip. that might draw them out or maby try and get some fresh sea lettuce from the lfs its fairly common, cheap, and easy to get
are you all seeing lip marks on the glass? they like to eat the algae off the glass. they like the diatomic algae. my bicolour will eat just about anything. just give them a little time. i bet they are munching on algae when you are not looking.