The versatility of quantum well infrared photodetector (QWIP) structures allows for voltage tunable detection. However, the existing designs generally suffer from limited range of tunability and substantial spectral cross-talk. In this work, we demonstrated a QWIP structure, which is capable of detecting four widely separated and narrowly peaked individual bands under different bias. The detection peaks range from mid-wavelength to long-wavelength and are centered at 4.5, 5.3, 8.3, and 10.4 μm, respectively, with Δλ/λ < 0.14. With f/1.2 optics, the detector is BLIP at 100K, 80K, 60K and 50K respectively for the increasing wavelengths. This four-color detector consists of two stacks of voltage tunable materials that are separated by a middle contact layer. Each material is designed to detect at two specific wavelengths depending on the bias polarity. In the present design, the upper stack switches between 5.3 μm and 10.4 μm, while the bottom stack switches between 4.5 μm and 8.3 μm. By applying different bias to the top and bottom contacts relative to the common middle contact, the optical signal for each color can be readout at the two contacts sequentially. The tunable material is made of repeated unit cells, and each unit cell contains two different superlattices separated by a thick barrier. Based on this design, the detection peaks can be randomly selected between 3 μm and 20 μm, and each peak can vary from narrow band to broadband. The present detector design thus improves the QWIP technology in multi-color detection.