Assembly of lipid bilayers onto the surface of silica particles allows for the surface composition and charge of the particles to be tuned continuously over a wide range. The collective behavior of these systems depends strongly on the properties of the coating membrane with subtle changes in the surface chemistry resulting in macroscopic changes in the order within the system. Using a combination of optical imaging techniques we are able to monitor both the colloid structure and the surface potential in electrostatically levitated colloidal monolayers composed of lipid-coated particles. We observe that interactions can be tuned, from repulsive to long-range attractive. The collective behavior is asymmetric with respect to the sign of the surface potential. Incorporation of membrane-associated receptors to the lipid coating allows for biofunctional studies. We observe that binding of protein to the membrane receptors results in macroscopic changes in monolayer ordering thereby providing a label-free method for monitoring molecular interactions on membrane surfaces.