A study was conducted to investigate the pseudomorphic transformation of three-dimensionally ordered macroporous (3DOM) inverse opal tungsten oxide (WO3) into tungsten carbide. Inverse opal WO3 was transformed into tungsten carbide, as it provided significant advantages for catalytic and electrocatalytic applications. 3DOM tungsten carbide was also found to be suitable for studying the morphological replication capabilities/limitations of pseumorphic transformation reactions. The extent of pseudomorphic retention in inverse opal materials was also evaluated, by comparing changes in their opalescent colors before and after reactions. The color was produced from the diffraction of visible light, by the periodic geometry of inverse opals and shifted in response to changes in refractive index and pore size. These factors have of the 3DOM materials influenced their use in exploring the resolution limitations and overall scope of pseudomorphic transformation reactions.