Colorimetric　enzyme-linked　immunosorbent　assay　utilizing　3′-3-5′-5-tetramethylbenzidine(TMB)　as　the　chromogenic　substrate　has　been　widely　used　in　the　hospital　for　the　detection　of　all　kinds　of　disease　biomarkers.　Herein,　we　demonstrate　a　strategy　to　change　this　single-color　display　into　dual-color　responses　to　improve　the　accuracy　of　visual　inspection.　Our　investigation　firstly　reveals　that　oxidation　state　of　3′-3-5′-5-tetramethylbenzidine　(TMB　2+)　can　quantitatively　etch　gold　nanoparticles.　Therefore,　the　incorporation　of　gold　nanoparticles　into　a　commercial　TMB-based　ELISA　kit　could　generate　dual-color　responses:　the　solution　color　varied　gradually　from　wine　red　(absorption　peak　located　at　∼530　nm)　to　colorless,　and　then　from　colorless　to　yellow　(absorption　peak　located　at　∼450　nm)　with　the　increase　amount　of　targets.　These　dual-color　responses　effectively　improved　the　sensitivity　as　well　as　the　accuracy　of　visual　inspection.　For　example,　the　proposed　dual-color　plasmonic　ELISA　is　demonstrated　for　the　detection　of　prostate-specific　antigen　(PSA)　in　human　serum　with　a　visual　limit　of　detection　(LOD)　as　low　as　0.0093　ng/mL.　©　The　Author(s)　2016.