Electrochromic materials with dynamic color change and optical modulation have potential applications in the fields of automotive anti-glare mirror, smart window, low-power display, and electronic paper, attracting worldwide attention. NiO and MnO₂ are typical anodic coloration materials with a comfortable neutral tone. However, the low transmittance of single NiO or MnO₂ films in bleaching states leads to small optical modulation. Herein, a porous nickel-manganese layered double hydroxide (NiMn-LDH) film with neutral color for visible electrochromic application was prepared. The NiMn-LDH films were grown directly on fluorine-doped tin oxide (FTO) conductive glass substrates by a one-step solvothermal method using NiCl₂·6H₂O and MnSO₄·H₂O as the raw materials. The crystalline phase and micromorphology of the as-grown NiMn-LDH films were characterized and the electrochromic and electrochemical performances were also investigated. The results indicate that the film grown by solvothermal method is composed of NiMn-LDH nanosheets with porous surface morphology, leading to a large optical modulation of 61.9% at 550 nm. The coloration and bleaching time are calculated to be 15.8 and 13.2 s, respectively. A high coloration efficiency of 63.1 cm²·C^-1 is also achieved for the as-grown NiMn-LDH nanosheet film. Meanwhile, the NiMn-LDH film electrode demonstrates good cycle stability, retaining 87.0% of its maximum optical modulation after 160 cycles. Furthermore, the NiMn-LDH film electrode delivers an area capacitance of 10.0 mF·cm^-2 at a current density of 0.1 mA·cm^-2. These results consolidate that the as-prepared NiMn-LDH film electrode is a promising candidate for both electrochromic and energy-storage applications.