This paper presents the use of polyelectrolyte-decorated amyloid fibrils as gate electrolyte in electrochromic electrochemical transistors. Conducting polymer alkoxysulfonate poly(3,4-ethylenedioxythiophene) (PEDOT-S) and luminescent conjugate polymer poly(thiophene acetic acid) (PTAA) are utilized to decorate insulin amyloid fibrils for gating lateral poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) electrochemical transistors. In this comparative work, four gate electrolytes are explored, including the polyelectrolytes and their amyloid-fibril complexes. The discrimination of transistor behaviors with different gate electrolytes is understood in terms of an electrochemical mechanism. The combination of luminescent polymers, biomolecules and electrochromic transistors enables multi functions in a single device, for example, the color modulation in monochrome electrochromic display, as well as biological sensing/labeling.