Abstract: A colorimetric detector for chemical and biological agents or toxins is made of a giant unilamellar vesicle (GUV) having a membrane bilayer which is polymerized to stabilize the giant unilamellar vesicle and to provide extended conjugated polymer backbone, and the GUV has at least one incorporated molecular recognition site for the chemical and biological agents or toxins. The GUVs are about 10-300 microns and preferably made of a polymerizable diacetylenic GUV where the acyl chains are crosslinked. When the agents or toxins bind to the recognition site the detector exhibits a color change. The detector can be used in a colorimetric detector apparatus where the samples can be present in air or in water.