Which of the following compounds is not colored yellow?

In the complex Zn2[Fe(CN)6], the iron atom has an oxidation state of +2. Its outer electronic configuration is 3d6. Cyanide ligand (CN⁻) is a strong ligand and it causes spin pairing. Hence, all the 6 electrons in 3d are paired and present in t2g level. Since there is no unpaired electron, the complex is diamagnetic and colorless. K3[Co(NO2)6] is yellow due to the presence of unpaired electrons in cobalt. BaCrO4 is yellow due to the chromate ion (CrO4²⁻). (NH4)3[As(Mo3O10)4] is also colored, likely due to the presence of molybdenum in a mixed oxidation state. Therefore, Zn2[Fe(CN)6] is the compound that is not colored yellow.